Ion Science MiniPID 2 User manual

Brand: Ion Science

Model: MiniPID 2

Type: User manual

MiniPID 2 (3PIN)

Instrument User Manual V1.3R

MINIPID 2 3PIN MANUAL Ion Science Ltd

Page 3 of 28

Declaration of conformity

Manufacturer: Ion Science Ltd, The Hive, Butts Lane, Fowlmere, Cambridge, SG8 7SL

Product: MiniPID Std or MiniPID Reg Revision 2

Product Description: Intrinsically safe photo-ionisation sensor for volatile organic compounds

DIRECTIVE 2014/34/EU ATEX

Identification: II 1G Ex ia IIC T4 Ga (-40

C ≤ Ta ≤ +55

C) @ 1.1W limitation

(-40

C ≤ Ta ≤ +65

C) @ 0.9W limitation

Notified Body: Baseefa Ltd, 1180, Buxton, UK

Underwriters Laboratories, USA

EC Type Examination Certificate(s)

Baseefa07ATEX0060U – latest supplement Baseefa 07ATEX0060U-7issued 16th December 2015

Ref Baseefa Cert Report 04(c)0865, ExTR07.0146/00, ExTR07.0181/00,

ExTR08.0135/00, ExTR09.0195/00, ExTR12.0273/00, ExTR15.0368/00,

ExTR11.0231/00

IECeX BAS 07.0030U – latest revision No 8 issued 1

August 2017

Ref IECeX Text Reports GB/BAS/EX TR07.0056/01 TR07.0146/00

TR07.0181/00 TR08.0135/01 TR09.0195/00 GB/BAS/EX TR11.0231/00

GB/BAS/EXTR12.0273/00 GB/BAS/EXTR15.0368/00

Standards

BS EN 60079-0:2012+A11:2013 Electrical Apparatus for Potentially Explosive Atmospheres – General

Requirement

BS EN 60079-11:2012 Explosive Atmospheres - Equipment Protection by Intrinsic Safety ‘i’

BS EN 61010-1:2010 Safety requirements for electrical equipment for measurement, control and

laboratory use – General requirements

UL913; 2

Edition Intrinsically safe apparatus and associated apparatus for use in Class I, II, III,

Division 1, Hazardous (Classified) Locations

CSA-C22.2 No157-92 Intrinsically safe and non-incendive equipment for use in Hazardous Locations

(Update 2)

Other Standards

BS EN ISO 9001:2015 Quality Management Systems – Requirements

BS EN 80079-34:2011 Potentially Explosive Atmospheres – Application of Quality Systems

On behalf of Ion Science Ltd, I declare that, on the date this product accompanied by this declaration is

placed on the market, the product conforms with all technical and regulatory requirements of the above listed

directives.

Name: Mark Stockdale Position: Technical Director

Signature: Date: 22nd March 2017 Doc. Ref. 846238 issue

MINIPID 2 3PIN MANUAL    Ion Science Ltd 
 Page 4 of 28 
Contents                         
 
Declaration of conformity ................................................................................................. 3 
Statements ......................................................................................................................... 5 
Responsibility for Use ....................................................................................................... 5 
Introduction ........................................................................................................................ 6 
Applications ....................................................................................................................... 6 
Features .............................................................................................................................. 6 
How does it work? ............................................................................................................. 7 
What is a volatile organic compound (VOC)? ................................................................... 7 
Response Factors .............................................................................................................. 8 
What is a response factor? ............................................................................................... 8 
Physical properties ............................................................................................................ 9 
Instrument interfacing ..................................................................................................... 10 
Mechanical installation .................................................................................................... 10 
Sealing the MiniPID 2 ..................................................................................................... 10 
Suggested Pneumatic Installation ................................................................................... 10 
Instrument interfacing – Best Practice .......................................................................... 11 
Electrical Installation ....................................................................................................... 12 
Electrical installation ....................................................................................................... 13 
Power-up surge .............................................................................................................. 13 
Analogue output .............................................................................................................. 13 
Error states ..................................................................................................................... 13 
Electrical Installation – Best Practice ............................................................................ 14 
PCB layout for EMC noise reduction............................................................................... 14 
General – Best Practice ................................................................................................... 15 
Intrinsic Safety ................................................................................................................. 16 
Schematic Block diagram ............................................................................................... 17 
Intrinsic Safety circuit implementation ............................................................................. 17 
Specification .................................................................................................................... 18 
Common Electrical Specifications: .................................................................................. 18 
Environmental Effects ..................................................................................................... 20 
Natural physical effects of humidity................................................................................. 20 
Temperature ................................................................................................................... 21 
Maintenance ..................................................................................................................... 22 
When does my MiniPID 2 require maintenance? ............................................................ 22 
When do I clean the MiniPID 2 lamp? ............................................................................. 22 
When do I replace the MiniPID 2 electrode stack? ......................................................... 22 
When do I replace the MiniPID 2 lamp? .......................................................................... 22 
Removing electrode stack and lamp ............................................................................... 22 
Cleaning the MiniPID 2 Lamp ......................................................................................... 23 
Re-fitting MiniPID 2 electrode stack and lamp ................................................................ 24 
Instrument warranty and service .................................................................................... 24 
Warranty ......................................................................................................................... 25 
Service ............................................................................................................................ 25 
Contact Details ............................................................................................................... 25 
Parts List .......................................................................................................................... 26 
Spares ............................................................................................................................... 27 
Manual log ........................................................................................................................ 28 

MINIPID 2 3PIN MANUAL Ion Science Ltd

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Statements

Responsibility for Use

Inadequate performance of the gas detection equipment described in this manual may not necessarily be

self-evident and consequently equipment must be regularly inspected and maintained. Ion Science

recommends that personnel responsible for equipment use institute a regime of regular checks to ensure it

performs within calibration limits, and that a record be maintained which logs calibration check data. The

equipment should be used in accordance with this manual, and in compliance with local safety standards.

Legal Notice

Whilst every attempt is made to ensure the accuracy of the information contained in this manual, Ion Science accepts no liability for errors or omissions, or any consequences

deriving from the use of information contained herein. It is provided "as is" and without any representation, term, condition or warranty of any kind, either express or implied. To the

extent permitted by law, Ion Science shall not be liable to any person or entity for any loss or damage which may arise from the use of this manual. We reserve the right at any time

and without any notice to remove, amend or vary any of the content which appears herein.

MINIPID 2 3PIN MANUAL Ion Science Ltd

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Introduction

MiniPID 2 is a miniature photoionisation (PID) sensor. Sample gas freely diffusing through the filter membrane

is exposed to deep ultraviolet light generated by a lamp within the sensor. The emitted light ionises targeted

gases in the sample so they can be detected by the gas detector and reported as a concentration (eg ppb,

ppm or mg/m

Chemicals such as volatile organic compounds (VOCs) with an ionisation energy less than or equal to the

UV energy of the PID (10.0, 10.6 or 11.7 eV) will be detected by the MiniPID 2.

The MiniPID 2 sensor is offered in five models having the guaranteed range of operation below (isobutylene

equivalent). They are virtually insensitive to humidity changes, providing unparalleled performance in a

variety of applications.

The MiniPID 2 PPM 100 ppb to 6,000 ppm.

The MiniPID 2 PPB 1 ppb to 50 ppm.

The MiniPID 2 HS 0.5 ppb to 4 ppm.

The MiniPID 2 10 eV 5 ppb to 100 ppm.

The MiniPID 2 11.7 eV 100 ppb to 100 ppm.

Please contact Ion Science at ionscience.com for a comprehensive list of response factors for various VOCs.

The MiniPID 2 sensor pack includes a sensor incorporating a lamp, lamp driver, amplifier circuitry, removable

electrode stack with particulate filter and electrode stack removal tool.

Features

 Patented guard electrode for excellent

humidity immunity

 Reliable lamp – illuminates at low

temperatures

 Superior lamp life

 User-replaceable electrode stack keeps

your PID working, even after bad

contamination

 Intrinsically safe (ATEX, IECeX, UL, CUL)

 Bulb out error detection (MiniPID 2 PPM

only)

Applications

 Industrial hygiene & safety

monitoring

 Soil contamination and remediation

 Hazmat sites and spills

 Low concentration leak detection

 EPA Method 21 and emissions

monitoring

 Arson investigation

 Indoor air quality monitoring

MINIPID 2 3PIN MANUAL Ion Science Ltd

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How does it work?

The Ion Science MiniPID 2 measures volatile organic compounds (VOCs) in air by photoionisation detection

(PID), which is shown schematically below. Test gas (1) is presented to the membrane filter at the top of the

photoionisation cell and freely diffuses into and out of the underlying chamber formed by the filter, housing

walls, and a UV lamp window. The lamp emits photons (shown by arrows) of high energy UV light,

transmitted through the window. Photoionisation occurs in the chamber when a photon is adsorbed by the

molecule, generating two electrically charged ions, one positively charged, X

, and one negatively charged,

(2a). An electric field, generated between the cathode and anode electrodes, attracts the ions (2b). The

resulting current, which is proportional to the concentration of the VOC, is measured and used to determine

the gas concentration. The MiniPID 2 includes a third fence electrode (patented) to ensure that the amplified

current does not include significant contributions due to other current sources such as water condensation on

the chamber walls.

What is a volatile organic compound (VOC)?

A volatile organic compound, or VOC, is a carbon-containing chemical, which is significantly or completely

vaporised at ambient temperatures.

What volatile organic compound (VOCs) are sensed by MiniPID 2

Most VOC’s can be detected by MiniPID 2. Notable exceptions are low molecular weight hydrocarbons. Each

VOC has a characteristic threshold energy of light (photon energy) which, when directed at the VOC, causes

it to fragment into ions. This is called the Ionisation Energy, or IE. VOCs are ionised (and hence detected) if

light of photon energy greater than the IP interacts with the gas sample. The peak photon energy generated

in a detector depends on the PID lamp used: Krypton = 10.6 eV or Argon = 11.7 eV. Hence, the use of an

argon lamp leads to detection of the largest range of volatile compounds, while using a Krypton lamp can

increase selectivity. Lamps of a particular type do not typically vary in spectral fingerprint, so relative responses

to a particular gas, eg benzene, to a particular lamp, e.g. krypton, does not vary from lamp to lamp. However,

the intensity of lamps does vary to some extent, leading to a difference in absolute response to the calibration

gas.

Sufficient volatility of a compound is also essential for measurement by PID as with any other detector. A

fairly large molecule such as alpha-pinene, (a constituent of turpentine), saturates in air at about 5000 ppm

at 20

C; this is the maximum concentration at which the compound will usually be detected. Some

compounds, for example, machine oils and agrochemicals - generate only a few ppm of vapour at ambient

temperatures; it is more difficult to detect these compounds in air. For further information on the sensing

capabilities of MiniPID2 please refer to the technical application note library on our website.

To anode

Lamp gas, eg

krypton

Lamp

window

Test gas

Lamp

body

Cathode

Anode

Fence electrode

Photon

To cathode

MINIPID 2 3PIN MANUAL Ion Science Ltd

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Response Factors

What is a response factor?

Our PIDs are calibrated using isobutylene, but the PID is a broadband VOC detector with a sensitivity that

differs for each VOC. Response Factors are used to compensate for these differing sensitivities.

A response factor (RF) is a number which relates the MiniPID 2 response to a particular VOC relative to

isobutylene. If you know what VOC you are measuring then multiplying the displayed concentration by the

RF of the VOC will result in the actual concentration of VOC.

Example: Toluene

 A sensor is calibrated using isobutylene and found to have a sensitivity of 1 mV ppm

-1

 If the sensor is exposed to 100 ppm isobutylene the output will be 100 mV.

 Toluene is known to generate twice the response of isobutylene.

 In order to correct the toluene response it is multiplied by the response factor for toluene of 0.56.

 If the sensor is exposed to 100 ppm toluene then the displayed uncorrected concentration will be 200 ppm

isobutylene. The corrected concentration would be 200 multiplied by the RF, 0.56, which gives the correct

result of 100 ppm toluene.

If response factors are programmed into an instrument, you are able to specify a volatile compound, and the

instrument will internally compensate for the response factor corresponding to that volatile, and display and

record the corrected volatile concentration.

VOC mixtures

Occasionally you will be measuring a mixture of VOCs. If the total concentration is within the linear range of

the PID, then it is reasonable to assume that the concentrations are additive without interference between

the different VOCs:

The correction factor for a gas mix containing PID detectable gases A, B, C… with response factors RF(A),

RF(B), RF(C), in fractional proportions a:b:c is given by:

RF mix = 1/[a/RF(A) + b/RF(B) + c/RF(C)…]

Example:

A gas mix to be monitored contains 1 part isopropanol to 4 parts acetone:

Chemical name

Fractional composition

Isopropanol

4.0

0.2

Acetone

1.17

0.8

Therefore the RF of the mix will be:

RF mix = 1/[(4.0 x 0.2) + (1.17 x 0.8)]

= 1/(0.8 + 0.936)

= 0.58

Important: remember that if you are measuring a combination of VOCs then accurate measurement of one

of these VOCs will be difficult; without careful data analysis, you will get only a RF averaged measurement.

Be cautious when reporting actual VOC concentration if you know that there may be several VOCs present.

MINIPID 2 3PIN MANUAL Ion Science Ltd

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Physical properties

LEL equivalent

mechanical format

Base view

Outside dimensions and pin

configuration as per industry

standard series 4 LEL sensor

Pin Details

1 Positive Supply Voltage

2 Signal Output

3 0V Ground

HS variant

All other models

MINIPID 2 3PIN MANUAL Ion Science Ltd

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Instrument interfacing

Mechanical installation

The mechanical considerations have been made simpler by designing compatibility with the standard LEL

sensor configuration, thus it is possible to plug the MiniPID 2 into a standard 20mm diameter LEL sensor

position and the MiniPID 2 detector will operate correctly, provided the OEM external signal conditioning circuit

can operate under the stated output specification range of the MiniPID 2.

Always ensure that the interconnect pins are fully seated and that the sensor is fully secure to prevent

unintentional movement or removal of the sensor by those unauthorised to do so.

Sealing the MiniPID 2

The MiniPID 2 is designed to provide a good sealing area on the top face of the MiniPID 2. It is important that

your sampling line is well sealed to the MiniPID 2 when measuring VOCs using a downstream pump. Refer

to the data sheet to ensure that you are sealing properly the PID without covering the gas access area.

The sealed cavity is defined by the window face at one end, through to the volume that contains the electrode

stack arrangement and up to the PID filter front face. It is at this front face the OEM designer must seal upon,

ensuring that the seal lies within the three segmented arcs visible on the front face. This gives a very small

detector cavity of about 15 mm

that opens up many exciting possibilities for analytical work in pump drawn

systems.

Due to the potential for minor leakage through the layers within the cell do not exceed 500 Pa (5 mbar)

differential pressure between the PID and the gas detector internal cavity. This will ensure good signal integrity

(within 1%). Typically 5000 Pa (50 mBar) gives (10%).

Suggested Pneumatic Installation

The MiniPID 2 can used in open aspirated systems or in applications requiring natural diffusion.

Avoid pressurising the MiniPID 2 beyond +/- 50 mBar pressure.

An O-ring can be used to seal a manifold against the MiniPID electrode stack as suggested in the diagram

above.

Important note:

While every care has been taken to ensure that the lamp sits abutted against the underside of the visible

electrode, always ensure that the lamp is firmly pushed up against the underside of the visible electrode.

Should the lamp not firmly abut the front electrode (relative to the lamp) then the user will experience severe

degradation in accuracy (combined reduced signal levels and poorer linearity at high VOC concentrations).

Incorrect abutment will also cause a loss in pneumatic sealing.

MINIPID 2 3PIN MANUAL Ion Science Ltd

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Instrument interfacing – Best Practice

MiniPID 2s have a very small sample volume, so this family of PIDs has fast response in both diffusion and

pumped gas modes. When designing the gasket between the PID and your gas sampling/diffusion access,

consider the following rules:

 Diffusion mode is ideal for this sensor design.

 Seal around the gas access port (with the white dust filter) using a gasket with an inner diameter of

6mm and an external diameter of 9.0mm. The inner diameter can be reduced to 4mm to further

increase response time, but careful alignment is required.

 Use the correct sealing material: the gasket should be closed cell foam or moulded rubber which

does not adsorb the VOCs you will be measuring. Preferred materials are fluoroelastomers and

fluorosilicones (beware of outgassing if pellistors are nearby), but lower cost seals may be adequate.

 Do not seal on the external diameter of the PID (20mm diameter). This gives water access to the

electrode stack / PID cell seal, encourages turbulence, increases gas volume (reducing response

time) and compresses the outside diameter of the PID, which is designed for compression near the

gas access, not at the external diameter.

 Avoid pressure differentials. The PID allows clearance and gas access between the lamp and PID

cell, so if the sensing area above the cell is positively pressurised, then sampled gas will be forced

past the lamp, encouraging contaminant deposition on the outside of the lamp, reducing lamp

intensity and hence reducing sensitivity.

 Since the gas access port is off-center and to avoid shear forces on the seal, do not seal using a

screw-down fitting which shears the gasket, but compress the gasket with a fitting and then use

screws to fix the fitting in place: keying of the fitting is good practice.

 The white dust filter on the top of the PID allows maximum VOC access. If you will be operating in

atmospheres with high aerosol/ particulate concentration, then consider an additional filter.

 For pumped systems (see page 10) flow rate should be 300 sccm (0.3 L/m). If there is no pressure

differential between ambient pressure and the pressure in the cell and the flow is across the sensor,

encouraging laminar flow, then flow rate can be increased to 500sccm (0.5 L/m).

 If the pump is upstream of the PID, this will generate turbulent flow, which should be considered in

your design. Always try to achieve flow across the membrane to minimise shear velocity at the

membrane and maximise laminar flow.

 Minimise the restriction between the PID and ambient gas.

MINIPID 2 3PIN MANUAL Ion Science Ltd

Page 12 of 28

Electrical Installation

This section explains how to connect electrically the MiniPID 2 in your gas detector. Please also take careful

notice of the differences stated when a MiniPID 2 is used in a Safe Zone and where it might be also be used

in a flammable atmosphere (Intrinsically Safe operation).

Externally regulated voltage rail: Vs = 3.0 to 3.2 V, Vs = 3.2 to 3.6 V.

In this state, the cell must be supplied a stable source of voltage between 3.0 to 3.6 V (dependent on MiniPID

type). The internal voltage rail is determined by the externally supplied voltage, affecting lamp illumination and

other circuits, and therefore determining the sensor response. This allows the user to trim the sensor to their

particular requirements.

All lamps are tested to operate at the minimum supply voltage of 3.0 V before they leave the factory. A lower

supply voltage will extend lamp life and deliver decreased gas sensitivity, extending the measuring range of

the sensor and require less power. Conversely, a higher rail voltage will assist in lamp ‘start up’ from cold,

increase the lamp power and decrease lamp life.

Always follow manufacturer’s recommendations for their specific power supply regulators to ensure stable

regulation, because poorly designed regulator circuits can in a few instances cause power rail resonance at

temperatures of less than negative 20 degC.

Internally regulated voltage rail: V

= 3.6 to 18.0 V, V

= 3.6 to 10.0 V

In this state the MiniPID 2s can be operated from 3.6 and 18.0 V for non-intrinsically safe applications and 3.6

and 10.0 V for intrinsically safe applications. The signal stability is unaffected by external supply drift as the

sensor circuits are internally regulated to 3.3 V and the user is completely free to select the most convenient

supply for their needs.

The internally regulated sensor is very much unaffected by power variance and can tolerate 1 V changes at

low frequency. Clearly the designer should guard against high frequency transient spikes as these might punch

their way through the internal regulator control circuits.

IMPORTANT: ENABLING OR DISABLING THE INTERNAL VOLTAGE REGULATOR WILL INVALIDATE

SENSOR WARRANTY

MINIPID 2 3PIN MANUAL Ion Science Ltd

Page 13 of 28

Electrical installation

Power-up surge

The normal supply current of the MiniPID varies from about 20 mA at 3.0 V to about 32 mA at 3.6 V, however

the circuit has been designed to aid in the lamp strike by consuming more current at power-up to give about

a 40% increase in ignition voltage. This gives a consequential increase in start-up current of about 130 mA

for about 100 ms. This special technique improves the service life of lamps. Because of the increased

operating current at the time of power-up a staggered turn-on of at least 200 ms is recommended.

Analogue output

The output voltage range is from 0.0 V to (V

- 0.1) V for the externally regulated voltage range of V

= 3.0 to

3.6 V. The output voltage range is 0.0 to 3.2 V when using the internal regulation on a supply of 3.6 V to 18

V. The operating signal output signal is scaled from +50 mV because:

 The input amplifier has the best input bias current characteristics when biased at +50 mV.

 This allows the OEM external amplifiers to operate with their inputs above 0V for more flexibility.

 This allows the use of error status signal levels below the normal 50 mV base signal level. These

error status levels are listed below.

Error states

Voltages below 50mV indicate the following error conditions:

output voltage (mV)

Fault Condition

Recommended Action

PPM

PPB, HS, 10 eV,

11.7 eV

32 ± 1

n/a

Lamp not illuminated

Change or clean lamp

Electrode stack not fitted

correctly

Ensure electrode stack is fitted correctly

27 ± 1

41 ± 3

Oscillator not working

Change MiniPID

Misplaced electrode stack

Change electrode stack

18 ± 2

25 ± 2

Oscillator loaded

Change electrode stack and/or MiniPID

2 ± 2

Power removed

Check OEM supply voltage

Notes:

Voltages outside these limits are not rigorously defined. It is suggested that as a first action the electrode

stack should be replaced when an error state occurs.

The signal levels given are for an unloaded PID output. If the PID is connected to a loading circuit then the

output voltage will be reduced accordingly – please see “Equivalent Intrinsically Safe Circuit” for output

impedance

MINIPID 2 3PIN MANUAL Ion Science Ltd

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Electrical Installation – Best Practice

Faraday cage for EMC noise reduction

An electrically grounded Faraday cage is required for MiniPID 2s mounted near to, or on the outside of an

instrument for the sole reason of electro-static discharge that may falsely give a “lamp not illuminated” error

state. Electrical currents in the order of sub-picoamps generated within the sensing cell are being carefully

monitored by the internal electronics for a “lamp-out” occurrence, and any capacitive coupled EMC discharge

on an ungrounded case/covering can be transmitted to these circuits and cause a false “lamp not illuminated”

error message to be registered on the signal output line of the MiniPID 2. This will be seen by the signal output

dropping low to about 32 mV. The duration of this change will be dependent upon the severity of the close-

coupled EMC discharge. The error state is self-resetting, so in the absence of EMC interference normal

operation will resume.

This cannot be designed-out within the product because it is part of the signal and any attempt to stop this

other than by the use of a screening case over the whole product (particularly at the electrode stack) will also

effect VOC generated signal.

PCB layout for EMC noise reduction

To optimise the performance out of the MiniPID 2 it is recommended that micro-strip layout techniques be used

to reduce susceptibility to EMC noise:

 To minimise the externally created noise superimposing itself onto the signal the lines should be located

close to the ground plane, balanced and directly coupled to a differential input analogue-to-digital

Converter (ADC) or differential input amplifier.

 A separate signal 0V line should be connected direct to the 0V pin of the PID and run parallel with the

signal line to the differential input ADC or amplifier. This single pair of signal lines should ideally be

located between two ground planes or at least run for its full length directly over the top of a ground

plane.

 Since the PID responds in 50-100 ms, you can include an RC network on both signal lines located

directly at the input of the differential input ADC or amplifier to remove 100Hz (and higher frequency)

noise.

 While the MiniPID 2 has its own internal screening, it is possible to achieve maximal noise reduction if

the entire MiniPID 2 sensor is mounted within a Faraday cage, which should be electrically connected

to the ground plane.

MINIPID 2 3PIN MANUAL Ion Science Ltd

Page 15 of 28

General – Best Practice

Balance Gas

When calibrating, ensure that the gas carrier (e.g. nitrogen cylinder or compressed air) is clean - defined as

“zero air”. Lubricating oils in compressed air lines should be avoided as they will foul PIDs if exposed to the

gas stream for extended times.

Some gases absorb UV light without causing any PID response (e.g. methane, ethane). In ambient

atmospheres where these gases are present the measured concentration of target gas will be less than is

actually present. Methane absorbs UV strongly, so for accurate measurements in methane containing

atmospheres, calibrate with a calibration gas containing the expected methane concentration. 50% LEL

methane reduces the reading by up to 50%. Gases such as nitrogen and helium do not absorb UV and do

not affect the relative response.

High Backgrounds

The Offset Voltage specification provided on page 19 of the manual is the typical sensor output voltage

expected when the sensor is supplied with clean air and has stabilised. Sensor output voltages in clean air

will vary from sensor-to-sensor and should be calibrated out accordingly using best practices based upon the

required accuracy and application. This sensor-to-sensor variation is dependent upon electrode stack

condition, lamp output and variance in electronic circuitry.

After periods of storage or non-usage, the MiniPID 2 may be susceptible to baseline settlement issues. In such

an event, it is recommended that the MiniPID 2 Sensor is left powered in a clean air environment for an hour

or two. For detection at very low gas concentrations (ppb) after an extended epoch of storage the MiniPID 2

may require operation in clean air for several hours to get to a stable baseline reading.

The background increase is dependent upon cell contamination which can be one or more of the factors

given below (the first two points are highly dependent upon the type of usage).

 Temporary contamination within the layers of the electrode stack which may require some minutes of

lamp illumination to burn-off the debris.

 Excessive permanent contamination through salts (or the suchlike) deposited along the walls which

bridges the fence electrode and reduces its effectiveness. The cell needs to be replaced if this is

suspected to be the cause.

 A much lower signal caused by photo-ejection from the back-electrode that is used to monitor the

status of the lamp condition to create our error status messages.

This combined signal is part of the ‘lamp-out-detection’ circuit presently unique to this type of sensor and

thus allows for continuous real time ‘in-cell’ monitoring.

‘lamp-out detection’ failing to occur is likely due to a heavily contaminated electrode stack – where surface

leakage and/or salt build-up within the cell creates unwanted currents similar to that created by lamp

illumination. Always ensure a clean electrode stack is used. Excessive cell contamination can always be

checked with the lamp removed but with the electrode stack in place to give a lamp error status in normal

operation.

! Caution ! Note on Silicones:

PIDs are not permanently damaged by Silicones but they do potentially foul the windows of the lamps and

reduce response to some gases. This can usually be remedied by polishing the lamp window with alumina

powder. However, instrument manufactures incorporating the MiniPID 2 sensors should be careful to avoid

any silicones such as those which may occur in labels and moulding release agents for plastics. Over months

of storage the silicones may leach into the sensor and lead to window fouling and sensitivity lost.

MINIPID 2 3PIN MANUAL Ion Science Ltd

Page 16 of 28

Intrinsic Safety

Summary for use of the MiniPID 2 in intrinsic safe applications.

Maximum temperature for intrinsically safe operation.

MiniPID 2 is designed to have minimum response change over their full temperature range, and because

performance of potting compounds changes with temperature, there is no potting compound in the sensor.

However this meant serious design considerations were imposed on the MiniPID 2 for its T4 temperature

rating, due to the lack of internal space for components capable of operating at the 55C for 1.1 W T4 class

(60 C for 1.0 W and 65C for 0.9 W).

The MiniPID 2 may be plugged directly into an LEL sensor PCB position whose power is supplied by an

external 125 mA fuse for a T4 rating in an ambient temperature of up to 55C. The MiniPID 2 is not rated above

the power ratings given for the temperature limits because the internal zener diodes would exceed their rated

temperature rise based upon the 3W zeners’ die temperature rating at the stated maximum ambient

temperature when tested at the fused clamped current.

Summary for use of the MiniPID 2 in intrinsic safe applications.

1. External supply surge current must be limited to 3.3 A under fault conditions.

2. Depending upon maximum supply voltage, the MiniPID 2 may use a 125 mA fuse in the supply line

for 55C for 1.1 W T4 and a series resistor for reduced power limits for operation above 55C ambient

temperature.

3. Take note of the various maximum supply voltages that may become connected to any of the pins

under fault conditions.

4. Take note of the power limits of the various pins under fault conditions.

5. The capacitance is low and should not cause problems at these voltages.

6. If processing electronics are located in another zone, then barrier/ segregation resistors are required

in any signal lines.

7. Competent third party assessment is required on the final product.

8. MiniPID 2 Reg

Working near 10V should have signal and power rails infallibly isolated to ensure lumped capacitances

on an external short circuit does not exceed the safety current limit.

Possible Intrinsically safe installations Equivalent Intrinsic Safe circuit

MINIPID 2 3PIN MANUAL Ion Science Ltd

Page 17 of 28

Intrinsic Safety

Schematic Block diagram

Intrinsic Safety circuit implementation

It is very important to abide by the stated temperature, power, voltage and current ratings.

This product is designed to drop into a standard LEL sensor position, however:

LEL sensors take considerable current and are often zoned by a separate 125 mA fuse and other suitable

upstream voltage limiting devices. Depending upon the current required by the monitoring electronic circuits

the MiniPID 2 may either share the same zoned 125 mA fuse or the electronics can be located in another

zone whose power is supplied by another fuse.

If two zones are required, then very low current signals may be passed between the two zones by isolating

resistors to limit any potentially shared high current between the two zones thus maintaining separate zone

integrity.

MINIPID 2 3PIN MANUAL Ion Science Ltd

Page 18 of 28

Specification

Common Electrical Specifications:

Supply Voltage on pin 1 Ref to 0 V on pin 3

MiniPID STD Revision 2 supply V

3.3 V+ 0.3 V / - 0.1 V stable (noise free).

Current drawn (at V

= 3.3 V, 20

C) I

24 mA to 33 mA at V

= 3.3V,

Power consumption (at V

= 3.3 V) P 110mW (typical)

Peak current at power-up I

130 mA for 0.1 s maximum.

MiniPID Reg. Revision 2 supply V

3.6 V to 18 V (Non-IS) (variable) maximum.

Current drawn I

30 mA  3 mA (independent to V

)

Current Construction Drift I

ΔT

1.5mA/10°C typical

Voltage on Signal Output pin 2 Ref to 0 V on pin 3

Linear signal output: V

> 50 mV to Positive Supply Voltage (less

0.1V)

Stepped error states: V

< 40 mV

Output capacitance: C

1.0 uF through 4k7  + 0.11 uF at pin

Output resistance: R

6k3 

Output clamp: V

5V1 zener protected by 4k7  resistor.

Supplementary Intrinsically Safe Specifications:

 Approval

ATEX Approved Baseefa 07ATEX0060U UL Class 1 Div 1 Groups A, B, C, D T4

IECEx Approved BAS07.0030U Conforms to UL standard 913

II 1G Ex ia IIC T4 Ga Certified to CSA standard C22. 2 No. 157

Temperature range -40C ≤ Ta ≤55C

(note: Pi where Ta may be taken to 65°C)

Supply Voltage on pin 1 Ref to 0 V on pin 3

MiniPID Standard (with solder blob)

Voltage (Max) Ui 5.0 V

Current continuous (Max) Ii 220 mA

Power (Max) Pi 1.1 W @ +55 °C, 1.0 W @ 60C; 0.9 W @ 65C;

Current surge (Max) Surge < 3.3 A

Capacitance (Max) Ci 7.0 uF

Inductance (Max) Li 0 uH

MiniPID Regulated (without solder blob)

Voltage (Max) Ui 10.0 V

Current continuous (Max) Ii 220 mA

Power (Max) Pi 1.1 W @ +55 °C, 1.0 W @ 60C; 0.9 W @ 65C;

Current surge (Max) Surge < 3.3 A

Capacitance (Max) Ci 1.1 uF

Inductance (Max) Li 0 uH

Voltage on Signal Output pin 2 Ref to 0 V on pin 3 (line addition)

Voltage (Max) Ui 10.0 V

Current continuous (Max) Ii 10 mA

Power (Max) Pi 50 mW

Capacitance (Max) Ci 0.12 uF

Inductance (Max) Li 0 uH

Note: “Signal Output pin 3” Ci to be summed with “Supply Voltage pin 1” Ci above (not countable fault)

Special Conditions of Use

1. The component must be mounted within apparatus which provides ingress protection of at least IP20, protection against

impact, and protection against possible electrostatic charging of the plastic enclosure.

2. No conductive surfaces or items to be mounted within 10mm of the end cap (sensor face) unless either separated by 1mm

of solid insulation or connected to the 0V of the supply to the Component.

Warning:

The MiniPID sensor is an Intrinsically Safe device that contains limited energy storing components. An appropriate Intrinsically Safe

interface must be employed for use in hazardous locations noting power limitations and temperature ranges, and must be installed in

strict accordance with applicable safety codes and guidance given in the Manual. Failure to observe this warning can result in serious

injury and/or Property damage.

Version March 2017

MINIPID 2 3PIN MANUAL Ion Science Ltd

Page 19 of 28

Specification

For optimal performance, Ion Science recommends an operational voltage of 3.3V.

MniPID 2

PPB

MiniPID 2

PPM

MiniPID 2

10 eV

MiniPID 2

11.7 eV

Minimum Detection Level

1 ppb

100 ppb

0.5 ppb

5 ppb

100 ppb

Linear range

(above 1ppm, +/-3% deviation)

full range

100 ppm

full range

100 ppm

Minimum over-range

40 ppm

6000 ppm

3 ppm

100 ppm

1000 ppm

Typical sensitivity

(Linear range)

50 mV/ppm

0.7 mV/ppm

700 mV/ppm

25 mV/ppm

2.5 mV/ppm

Response Time in diffusion mode

(T90)

< 3 s

7 s

< 3 s

Offset Voltage

60-80 mV

50-65 mV

100-200 mV

55-70 mV

80-120 mV

Relative humidity range 0 to 99% RH, non-condensing

Product Specifications (general):

Lamp replacement User replaceable

Electrode stack User replaceable

On board filter (within disposable electrode stack) Removes liquids and particulates

Package Type Alphasense

CH-A3,City Technology

4P,

20 mm dia x 16.6 mm high

Weight < 9 g

Positional Sensitivity None

Warranty 12 months from date of shipment.

(Please see page 25 for details on extended warranty)

Patents US 7,046,012

EC 1474681

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1.05

10 100 1000

relaitive sensitivity

vs. 100 ppm

isobutylene, ppm

Typical MiniPID 2 PPM linearity

0.80

0.85

0.90

0.95

1.00

1.05

1.10

0.0 0.5 1.0 1.5 2.0 2.5 3.0

realative sensitivity

vs. 2 ppm

isobutylene, ppm

Typical MiniPID 2 HS linearity

MINIPID 2 3PIN MANUAL Ion Science Ltd

Page 20 of 28

Environmental Effects

Natural physical effects of humidity

Water is not itself detected by MiniPID 2, but it adsorbs a portion of the light that otherwise promotes a

response from a photoionisable gas. This means there is degree of signal attenuation based upon the

humidity of the gas sample,

The figures presented below indicate how the signal can be attenuated for the blue ‘ppm’ electrode stack as

the relative humidity increases. Note how the signal attenuation is greater for the same relative humidity as

the temperature increases as the adsorption of light by water increases. This effect will be the same for any

detectable gas.

100

0 20 40 60 80 100

percentage of response vs. RH = 0%

relative humidity, RH%

30 ºC

40 ºC

20 ºC

10 ºC

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Ion Science MiniPID 2 User manual

Brand: Ion Science

Model: MiniPID 2

Type: User manual

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Ion Science MiniPID 2 User manual

Ion Science MiniPID 2 User manual

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