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MiniPID 3PIN
Instrument User Manual V2.1
Part number: 846236
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Part number: 846236
MINIPID 3PIN MANUAL Ion Science Ltd
Unrivalled Detection. www.ionscience.com
Declaration of conformity
Manufacturer: Ion Science Ltd, The Way, Fowlmere, Cambridge, SG8 7UJ, UK
Product: MiniPID Std or MiniPID Reg
Product Description: Intrinsically safe photo-ionisation sensor for volatile organic compounds
Directive 94/9/EC ATEX
Identification: II 1G Ex ia IIC T4 (-40
(-40
o
C ≤ Ta ≤ +65
o
C) @ 0.9W limitation
o
C ≤ Ta ≤ +55
o
C) @ 1.1W limitation
Notified Body: Baseefa Ltd, 1180, Buxton, UK
Intertek, Cortland, NY 13045, USA
EC Type Examination Certificate(s)
Baseefa07ATEX0060U – latest supplement Baseefa 07ATEX0060U-6 issued 8th February 2013
Ref Baseefa Cert Report 07(A) 0688, 10(T) 0168
IECEx BAS 07.0030U – latest revision No 6 issued 8th February 2013
Ref IECEx Text Reports GB/BAS/EX TR07.0056/00 TR07.0146/00 TR07.0181/00
TR08.0135/00 TR03.0195/00
ETL & cETL Test Report No. 3176983CRT-003 Issued May 2010
Standards
BS EN 60079-0:2006 Electrical Apparatus for Potentially Explosive Atmospheres – General Requirement
BS EN 60079-11:2007 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; 2nd 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 9001:2008 Quality Management Systems – Requirements
BS EN 13980:2002 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: 11th August 2010 Doc. Ref. 846238
issue
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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
What is a response factor? ............................................................................................................................ 8
Physical properties .......................................................................................................................................... 9
Mechanical installation ................................................................................................................................. 10
Sealing the MiniPID ...................................................................................................................................... 10
Electrical Installation ..................................................................................................................................... 12
Selecting the correct supply voltage for your MiniPID ................................................................................. 12
Power-up surge ............................................................................................................................................ 13
Analogue output ........................................................................................................................................... 13
Error states (units shipped beginning 2009) ................................................................................................ 13
Zero offset correction ................................................................................................................................... 13
PCB layout for EMC noise reduction ........................................................................................................... 14
Temperature correction ................................................................................................................................ 15
Schematic Block diagram............................................................................................................................. 17
Intrinsic Safety circuit implementation .......................................................................................................... 17
Specification .................................................................................................................................................. 18
Common Electrical Specifications: ............................................................................................................... 18
Gas Detection Specifications (specific): ....................................................................................................... 19
Environmental Effects ................................................................................................................................... 21
Natural physical effects of humidity ............................................................................................................. 21
Maintenance ................................................................................................................................................... 22
When does my MiniPID require maintenance? ........................................................................................... 22
When do I clean the MiniPID lamp? ............................................................................................................. 22
When do I replace the MiniPID electrode pellet? ......................................................................................... 22
When do I replace the MiniPID lamp? ......................................................................................................... 22
Removing Mini Pellet and Lamp .................................................................................................................. 22
Cleaning the MiniPID Lamp ......................................................................................................................... 23
Re-fitting MiniPID pellet and lamp ................................................................................................................ 24
Instrument warranty and service ................................................................................................................. 24
Warranty ....................................................................................................................................................... 25
Service ......................................................................................................................................................... 25
Contact Details ............................................................................................................................................. 25
Manual log ...................................................................................................................................................... 27
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MINIPID 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.
Page 5 of 27
MINIPID 3PIN MANUAL Ion Science Ltd
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Features
Patented guard electrode for excellent
humidity immunity
Reliable lamp – illuminates at low
temperatures
Superior lamp life
User-replaceable electrode pellet keeps
your PID working, even after bad
contamination
Intrinsically safe (ATEX, IECEx, ETL, CETL)
Bulb out error detection (MiniPID 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
Introduction
MiniPID is a miniature photoionisation 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/m3).
Chemicals such as volatile organic compounds
(VOCs) with an ionisation potential less than or
equal to 10.6 eV will be detected by the
MiniPID.
The MiniPID can be installed in portable and stationary gas monitors that accept either Alphasense Ltd
CH-A3 or City Technology
same dimensional and electrical profile as pellistors (provided the electronics input circuit is designed to take
the sensor’s output range). This opens up an incredible variety of environmental and safety applications in
industrial, commercial and residential markets.
The MiniPID sensor is offered in two models having the guaranteed range of operation below. They are
virtually insensitive to humidity changes, providing unparalleled performance in a variety of applications.
The MiniPID PPM has a dynamic range of <100 ppb to >6,000 ppm (isobutylene).
The MiniPID PPB has a linear dynamic range of 1 ppb to >50 ppm (isobutylene).
Please contact Ion Science at www.ionscience.com for a comprehensive list of response factors for various
VOCs.
The MiniPID sensor pack includes a sensor incorporating a 10.6 eV lamp, lamp driver, amplifier circuitry and
removable electrode pellet with particulate filter and pellet removal tool.
TM
4P pellistor cells, providing complete PID capability in a package that has the
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TM
MINIPID 3PIN MANUAL Ion Science Ltd
Unrivalled Detection. www.ionscience.com
Lamp gas, eg
krypton
Lamp
window
Test gas
Lamp
body
Fence electrode
2
2b
2a
Y
X
+
Photon
Copyright Ion Science Ltd, 2007
To cathode
Y -
How does it work?
The Ion Science MiniPID 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,
Y- (2a). An electric field, generated between the cathode and anode electrodes, attracts 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 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?
Most VOC’s can be detected by MiniPID. 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 Potential, or IP. 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 Xenon 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 20oC; 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. ‘MiniPID response factors’ Application
Note lists VOCs by their common name and their sensitivity to a Krypton lamp, the most common lamp and
the lamp supplied with the MiniPID PPM and MiniPID PPB.
X
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Chemical name
RF
Fractional composition
Isopropanol
4.4
0.2
Acetone
0.7
0.8
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 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 0.5.
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, 0.5, 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 = a/RF(A) + b/RF(B) + c/RF(C)…
Example:
A gas mix to be monitored contains 1 part isopropanol to 4 parts acetone:
Therefore the RF of the mix will be:
RF mix = (4.4 x 0.2) + (0.7 x 0.8)
= 0.88 + 0.56
= 1.44
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.
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Patents:
US 7,046,012
EC 1474681
Input power:
3.3 V+ 0.3 V / - 0.2 V. Stable (noise free)
3.6 V to 10 V (IS) or 18 V (safe zone).
120mA max power-up surge for 0.3s
33mA typical under continuous operation
Ion Science Standard Versions:
MP3SM6LB MiniPID 3-pin ppm
(3V to 3.6V certified)
MP3SM6LC MiniPID 3-pin ppm
(3.6V to 10V certified)
MP3SM6LN MiniPID 3-pin ppm
(3.6V to 18V non certified)
MP3SB6FB MiniPID 3-pin ppb
(3V to 3.6V certified)
MP3SB6FC MiniPID 3-pin ppb
(3.6 to 10V certified)
MP3SB6FN MiniPID 3-pin ppb
(3.6 to 18V non certified)
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
Hazardous Locations Approvals:
ATEX Approved Baseefa 07ATEX0060U
IECEx Approved BAS07.0030U
II 1G Ex ia IIC T4
Intertek
Class 1 Div 1 Groups A, B, C, D T4
Conforms to UL standard 913
Certified to CSA standard C22. 2 No. 157
-40°C ≤ Ta ≤ 55°C 1.1 W (to 65°C @ 0.9 W)
Version MAY 2010
Physical properties
Note: Hashed area is the preferred sealing location for an O’Ring.
Bullet points of distinction:-
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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 into a standard 20mm diameter LEL sensor
position and the MiniPID detector will operate correctly, provided the OEM external signal conditioning circuit
can operate under the stated output specification range of the MiniPID.
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
The MiniPID is designed to provide a good sealing area on the top face of the MiniPID. It is important that
your sampling line is well sealed to the MiniPID 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 pellet
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 mm3 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%).
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.
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Instrument interfacing – Best Practice
MiniPIDs 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
pellet 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.
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Soldered
Unsoldered
(intrinsically safe
environment)
Unsoldered
(Non-intrinsically
safe environment)
MiniPID PPM, Vs
3 to 3.6 V
3.6 to 10 V
3.6 to 18V
MiniPID PPB, Vs
3 to 3.6 V
3.6 to 10 V
3.6 to 18V
Checking the quality of
solder joint
Set DVM to resistance
Pins 1 to 3 2 k
(either way around)
Pins 1 to 3 > 1 M
(either way around)
Pins 1 to 3 > 1 M
(either way around)
Electrical Installation
This section explains how to connect electrically the MiniPID in your gas detector. Please also take careful
notice of the differences stated when a MiniPID is used in a Safe Zone and where it might be also be used in
a flammable atmosphere (Intrinsically Safe operation).
Selecting the correct supply voltage for your MiniPID
The MiniPID module is protected from power supply reversal on any pins provided the supply is limited to the
rated voltage and the source current is limited to 150mA over several minutes. The supply is either internally
or externally regulated, depending upon the infilling with solder a small circular ‘solder well’ located on the
underside of the sensor.
Note: The solder needs to bridge from the bottom to the upper layer but need not fill the hole completely.
Supply voltage states, as circumscribed by infilling of the ‘solder well’.
WARNING: Please also note intrinsic safety constraints on supply voltage as given elsewhere.
Externally regulated voltage rail: Vs = 3.0 to 3.6 V.
In this state, the cell must be supplied a stable source of voltage between 3.0 to 3.6 V (ideally 3.1 V). 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 a minimum supply voltage of 3.0 V before they leave the factory. However,
as lamps age, the minimum required operating voltage slowly increases until the lamp requires a voltage
higher than the voltage rail supplied. Therefore a lower supply voltage will curtail lamp life and deliver
decreased gas sensitivity, but it will extend the measuring range of the sensor and of course require less
power. Conversely, longer lamp usage by having a higher rail voltage to assist in lamp ‘start up’ from cold
against the increased lamp power giving a less linear detection for high VOC concentrations
It is recommended that the power supply is stable to within 10 mV (high frequency spikes can be 10 times
greater than this). This will ensure that the digital drive circuit for the rf lamp oscillator remains in resonance,
maintaining a stable lamp intensity.
Internally regulated voltage rail: Vs = 3.6 to 18.0 V, Vs = 3.6 to 10.0 V
In this state the MiniPIDs 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.
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output voltage (mV)
Fault
Action
32 ±4
Lamp not striking
Change or clean lamp
22 ±6*
Oscillator not working
Change pellet and/or MniPID
2 ±2
Power removed
Check OEM supply voltage
Electrical installation
Power-up surge
While the MiniPID takes only 33 mA 7 mA under normal operation over the full voltage supply, there is a
power-up surge of about 120 mA (maximum) for about 150 ms while the MiniPID seeks resonance, thus
consuming more current at power-up.
Analogue output
The output voltage range is from 0.0 V to (Vs - 0.1) V for the externally regulated voltage range of Vs = 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 (units shipped beginning 2009)
Voltages below 50mV indicate the following error conditions:
*Either 5 Hz rectangular pulse to 50 mV or DC level
Note: Voltages outside these limits are not rigorously defined.
Zero offset correction
When determining VOC concentration, you must first subtract at least 50 mV from the MiniPID PPM signal,
and at least 55 mV from the MiniPID PPB signal. The increased output voltage above the stated 50 mV
minimum for the MiniPID is due to amplified pellet electrode stack leakage current. When the cell is dirty
then this current may increase to 52 mV for the MiniPID PPM or to 70 mV for the MiniPID PPB. The best way
to zero this offset voltage is to apply clean gas and reset the zero outside the MiniPID to become this new
offset voltage.
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Electrical Installation – Best Practice
An electrically grounded Faraday cage is required for MiniPIDs mounted near to, or on the outside of
an instrument for the sole reason of electro-static discharge that may falsely give a “Lamp-Out” error
state. This is because 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. Thus any
spurious capacitive coupled emc discharge on an ungrounded case/covering will be transmitted to
these circuits and cause a false “lamp-out” error message to be registered on the signal line of The
MiniPID output.
This will be seen by the signal step changing from about 52 mV to about 32 mV. The duration of this
change will be dependent upon the severity of the close-coupled emc discharge – it is self-resetting.
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 pellet)
will also effect VOC generated signal.
RF interference may affect the resonance detection only in the first second of power-up. Thus the
use of a Faraday cage will give more consistent calibrations because the same resonance frequency
will be detected each time on power-up.
Similarly circuits that use multiple MiniPIDs should have the power-up sequence for each module
staggered by about 0.5 s to ensure that power supply current surges that may cause voltage dipping
will not affect the common power rail to neighbouring modules. Or select the on-board regulator and
supply with 5V or more - to provide the local isolation of 3.3 V inside.
It is advised that if the MiniPID has been off for a period of time to pulse the power ON for about 2
seconds, then off and back on again to allow the transformer to stabilise to an ideal working state.
For maximum repeatability in sensitivity then with ambient temperature excursions of greater than +/-
8°C from power up state it is recommended to turn off for 0.5 seconds and then turn power back on
to re-set oscillator to resonant frequency. Typically the MiniPID will be ready within another 0.5
seconds after application power off. Often this is implicit in the applications.
PCB layout for EMC noise reduction
To optimise the performance out of the MiniPID 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-toDigital 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 has its own internal screening, it is possible to achieve maximal noise reduction if
the entire MiniPID sensor is mounted within a Faraday cage, which should be electrically connected to
the ground plane.
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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 th e
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
After periods of storage or non-usage, the MiniPID may be susceptible to baseline settlement issues. In such
an event, it is recommended that the MiniPID 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 may
require operation in clean air for several hours to get to a stable baseline reading.
The 2 mV and 20 mV increase from 50 mV is purely 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 pellet 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 pellet – 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 pellet is used. Excessive cell contamination can always be checked with the lamp
removed but with the pellet 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 sensors should be careful to avoid
any silicones such as those which may occur in labels and moulding release agaents for plastics. Over
months of storage the silicones may leach into the sensor and lead to window fouling and sensitivity lost.
Temperature correction
Increasing temperature increases slightly the PID sensitivity. At 50C the sensitivity is typically a few percent
higher than at 20C. At -20C sensitivity will be approximately 20% less than at 20C. It is always possible to
switch the sensor off and on during large temperature excursions to ensure the most accurate readings are
obtained.
Page 15 of 27
MINIPID 3PIN MANUAL Ion Science Ltd
Unrivalled Detection. www.ionscience.com
Intrinsic Safety
Summary for use of the MiniPID in intrinsic safe applications.
Maximum temperature for intrinsically safe operation.
MiniPID 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 for its T4 temperature
rating, due to the lack of internal space for components capable of operating at the 55C for 1.1 W T4 class
(60 C for 1.0 W and 65C for 0.9 W).
The MiniPID 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 55C. The MiniPID 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 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 may use a 125 mA fuse in the supply line for
55C for 1.1 W T4 and a series resistor for reduced power limits for operation above 55C 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 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
Version MAY 2010
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MINIPID 3PIN MANUAL Ion Science Ltd
Unrivalled Detection. www.ionscience.com
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 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.
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Unrivalled Detection. www.ionscience.com
MINIPID 3PIN MANUAL Ion Science Ltd
Specification
Common Electrical Specifications:
Supply Voltage on pin 1 Ref to 0 V on pin 3
MiniPID STD supply VS 3.3 V+ 0.3 V / - 0.2 V stable (noise free).
Current drawn (at VS = 3.3 V, 20 oC) IS 24 mA to 33 mA at VS = 3.3V,
Power consumption (at VS = 3.3 V) P 110mW (typical)
Peak current at power-up IM 120 mA for 0.3 s maximum.
MiniPID Reg. supply V
Current drawn IS 30 mA 3 mA (independent to VS)
Current Construction Drift IΔT 1.5mA/10°C typical
Voltage on Signal Output pin 2 Ref to 0 V on pin 3
Linear signal output: VSO > 50 mV to Positive Supply Voltage (less
0.1V)
Stepped error states: VEO < 40 mV
Output capacitance: C
Output resistance: RO 6k3
Output clamp: VOC 5V1 zener protected by 4k7 resistor.
S
O
1.0 uF through 4k7 + 0.11 uF at pin
3.6 V to 18 V (Non-IS) (variable) maximum.
Supplementary Intrinsically Safe Specifications:
Approval
ATEX Approved Baseefa 07ATEX0060U Intertek 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 Certified to CSA standard C22. 2 No. 157
Temperature range -40C ≤ Ta ≤55C (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 @ 60C; 0.9 W @ 65C;
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 @ 60C; 0.9 W @ 65C;
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)
Schedule of Limitations
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.
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 May 2010
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Unrivalled Detection. www.ionscience.com
0
20
40
60
80
100
120
10 100 1000 10000
liniearity, 100 ppm = 100%
isobutylene, ppm
MINIPID 3PIN MANUAL Ion Science Ltd
Specification
For optimal performance, Ion Science recommends an operational voltage of 3.3V.
Gas Detection Specifications (specific):
Transducer Details (ref Isobutylene) MiniPID PPB MiniPID PPM
Minimum Detection Level SD 1 ppb 100 ppb
Linear Range (±3% deviation) RL full range 100 ppm
Minimum over-range RO 50 ppm 6,000 ppm
Over range typical RT 80 ppm 10,000 ppm
Sensitivity (Linear range) S > 25 mV/ppm > 0.6 mV/ppm
Full Stabilisation Time (PPB 20 ppb, PPM 100 ppb) TS 5 min 10 s
Warm-up Time TW < 5 s < 5 s
Response Time in diffusion mode(t90) TR < 3 s < 3 s
Offset Voltage VOS 60-70 mV 50-54 mV
Gas Detection Specifications (general):
Target Gases VOC’s with ionisation potentials < 10.6 eV
Temperature related response variance ±10% between -20 and 60 oC, vs 20 oC response
(please check item 4 on page 14)
Relative humidity range 0 to 99% RH, non-condensing
Product Specifications (general):
Lamp replacement User replaceable (10.6 eV)
Electrode Pellet User replaceable
Onboard filter (within disposable pellet) Removes liquids and particulates
Package Type AlphasenseTM CH-A3,City TechnologyTM 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)
Typical MiniPID Linearity
Page 19 of 27
MINIPID 3PIN MANUAL Ion Science Ltd
Unrivalled Detection. www.ionscience.com
Environmental Effects
Temperature
Temperature effect on response of an MiniPID powered initially at 20oC, and continually powered during the
change of temperature to the indicated temperature. Error bars indicate variance between MiniPIDs.
Temperature effect on response of an MiniPID powered initially at 20oC. After temperature equilibration, the
MiniPID is repowered (powered of and on.) This confers less of a temperature effect and is recommended.
Page 20 of 27
MINIPID 3PIN MANUAL Ion Science Ltd
Unrivalled Detection. www.ionscience.com
90
91
92
93
94
95
96
97
98
99
100
0 20 40 60 80 100
percentage of response vs. RH = 0%
relative humidity, RH%
30 ºF
50 ºF
70 ºF
80 ºF
90 ºF
100 ºF
90
91
92
93
94
95
96
97
98
99
100
0 20 40 60 80 100
percentage of response vs. RH = 0%
relative humidity, RH%
30 ºC
40 ºC
20 ºC
10 ºC
Environmental Effects
Natural physical effects of humidity
Water is not itself detected by MiniPID, but it adsorbs a portion of the light that otherwise promotes a
response from a photoionisable gas.
The response of the MiniPID to humidity can be adjusted according to the figures presented below, for
Fahrenheit and Celsius temperatures. For example, it can be seen that at 80 oF and 90% relative humidity
(RH), a response is decreased from that in dry air by 20%. This effect will be the same for any detectable
gas.
Page 21 of 27
MINIPID 3PIN MANUAL Ion Science Ltd
Unrivalled Detection. www.ionscience.com
Maintenance
The electronics in the MiniPID sensor are designed to be maintenance-free and not accessible. Periodic
sensor maintenance is required for the Mini Pellet and the lamp.
When does my MiniPID require maintenance?
Your MiniPID lamp will need cleaning from time to time. How often depends
on the environment you are measuring. If you are measuring indoor air
quality where the VOC concentrations are low and there are few particulates,
then a monthly or even less frequent calibration may be adequate. However,
if you are measuring high VOC concentrations and particulates are present in
high concentration then check calibration frequently and when the PID has
lost sensitivity or error state shows, change the pellet as explained below.
Signs when the PID needs attention:
• If the baseline climbs after you zero the PID, then the pellet needs
replacing.
• If the PID becomes sensitive to humidity, then the pellet needs replacing.
• If the baseline shifts/unstable when PID moves, then pellet needs replacing.
• If sensitivity has dropped too much (note the change required when checking calibration), then the lamp
needs cleaning.
When do I clean the MiniPID lamp?
Cleaning of the MiniPID lamp is recommended as a first action when presented with an MiniPID that needs
cleaning. Use the procedure described below. It is recommended that a cell is recalibrated after cleaning a
lamp, especially if the cell has been used for a few months since the sensor was last used.
When do I replace the MiniPID electrode pellet?
The MiniPID pellet can last the lifetime of the MiniPID if used in clean environments, or may only last a
month if used in heavily contaminated sites. The pellet is a disposable item, so always hold a spare pellet if
you are working in a dirty environment. If the cell shows signs of contamination after the lamp window has
been cleaned, or is known to have been subjected to severe contamination, then it should be replaced.
Instructions for replacing the pellet are below. It is recommended that the MiniPID is recalibrated after
replacing the pellet.
When do I replace the MiniPID lamp?
An MiniPID will last a long time, typically a few thousand hours. Lamps are warranted for 12 months;
replacement bulbs are available and are not expensive to replace. The sensitivity of the MiniPID is
approximately in direct proportion to the lamp light intensity, so as a bulb fails, the response to a particular,
low gas concentration becomes more noisy.
Validity of lamp warranty is compromised if lamp cleaning maintenance is not followed and lamp has obvious
fouling/contamination.
Removing Mini Pellet and Lamp
Caution: Always use the Pellet removal tool. Any other tools (for example screwdrivers) may
damage your MiniPID body and will invalidate your warranty.
1. Gently remove the sensor from equipment.
2. Place the MiniPID, pellet side down, onto a clean surface.
3. Locate pellet removal tool into the side slots of the MiniPID and squeeze together until pellet and lamp
are released.
4. Lift carefully the MiniPID body away from the pellet and lamp.
5. Occasionally the lamp may be temporarily lodged in the cell and will need to be freed carefully with
tweezers.
6. Occasionally the small spring behind the lamp will come out when the lamp is removed from the sensor.
Simply replace it in to the sensor house.
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MINIPID 3PIN MANUAL Ion Science Ltd
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Hazard identification:
• May cause irritation of respiratory
tract and eyes
Storage:
• Keep container closed to
prevent water adsorption and
contamination.
Handling:
• Do not breathe in the powder. Avoid contact with skin,
eyes and clothing
• Wear suitable protective clothing
• Follow industrial hygiene practices: Wash face and
hands thoroughly with soap and water after use and
before eating, drinking, smoking or applying cosmetics.
• The powder carries a TVL(TWA) limit of 10 mg/m
3
Maintenance
Cleaning the MiniPID Lamp
Inspection of the lamp may reveal a layer of contamination on the detection window that presents itself as a
'blue hue.' To check for contamination, hold the lamp in front of a light source and look across the window
surface
Only clean the lamp using our recommended lamp cleaning kit and detailed instructions. To avoid
contaminating the sensor and affecting accuracy, do not touch the lamp window with bare fingers. You may
touch the lamp body with clean fingers.
MiniPID lamp cleaning kit A-31063
The vial of cleaning compound contains alumina (CAS Number 1344-28-1) as a very fine powder. Cleaning
should be undertaken in a well-ventilated area. A full material safety data sheet MSDS is available on
request from Ion Science Ltd. Key safety issues are identified below:
Cleaning the Lamp
Use of MiniPID lamp cleaning kit A-31063
1. Open the container of alumina polishing compound.
2. With a clean cotton bud, collect a small amount of the
powder.
3. Use this cotton bud to polish the PID lamp window. Use a
circular action, applying light pressure to clean the lamp
window. Do not touch the lamp window with fingers.
4. Continue polishing until an audible “squeaking” is made by
the cotton bud moving over the window surface. (usually
within 15 seconds)
5. Remove the residual powder from the lamp window with a clean cotton bud. Care must be taken not to
touch the tips of cotton buds that are to be used to clean the lamps as this may contaminate them with
finger print oil.
6. Ensure the lamp is completely dry and any visible signs of contamination are removed before refitting.
Discarding the MiniPID pellet
Discard the contaminated pellet. The pellet does not have any toxic components, but if it has been
contaminated by toxic materials, then show due care when disposing.
Page 23 of 27
MINIPID 3PIN MANUAL Ion Science Ltd
Unrivalled Detection. www.ionscience.com
Maintenance
Re-fitting MiniPID pellet and lamp
Caution! Never refit a damaged lamp
1. Place the lamp inside the O-ring seal in the pellet as illustrated. Twisting the lamp slightly during
insertion will help to ensure the lamp window is snug against the pellet’s front electrode. The lamp
should be freely supported by the O-ring.
2. Lay the pellet front face down on a clean, flat surface and then screw the lamp down into the O-ring
until it firmly abuts against the front electrode face – this is most important. Then bring the MiniPID
body carefully down over the lamp so as not to disturb its positioning within the pellet and then push
the body firmly onto the face down pellet so that it clicks into place.
3. Refit the sensor into the sensing equipment.
4. Re-calibrate the equipment in accordance with manufacturer’s instructions.
Page 24 of 27
MINIPID 3PIN MANUAL Ion Science Ltd
Unrivalled Detection. www.ionscience.com
US Office
Ion Science Inc.
4153 Bluebonnet Drive,
Stafford, TX
77477
US
Toll free: 001 877 864 7710
Email: info@ionscienceusa.com
Web: www.ionscienceusa.com
UK Head Office
Ion Science Ltd
The Way, Fowlmere
Cambridge
SG8 7UJ
UK
Tel: +44 (0)1763 207206
Fax: +44 (0) 1763 208814
Email: info@ionscience.com
Web: www.ionscience.com
German Office
Ion Science Messtechnik GMBH
Laubach 30
Metmann-Neandertal
40822
GERMANY
Tel: +49 2104 14480
Fax: +49 2104 144825
Email: info@ism-d.de
Web: www.ism-d.de
Instrument warranty and service
Warranty
Standard Warranty can be extended to up to 2 years on the MiniPID when registering your
instrument via our website: www.ionscience.com/instrument-registration
To receive your Extended Warranty, you need to register within one month of purchase (Terms
and Conditions apply). You will then receive a confirmation email that your Extended Warranty
Period has been activated and processed.
Full details, along with a copy of our Warranty Statement can be found by visiting:
www.ionscience.com/instrument-registration
Service
Ion Science is pleased to offer a number of service options on our MiniPID product range that
allow you to choose the instrument cover that best suits your needs.
At Ion Science we recommend that all of our gas detection instruments be returned for service
and factory calibration once every 12 months.
Contact Ion Science or your local distributor for service options in your area.
Find your local distributor by visiting: www.ionscience.com
Contact Details
Page 25 of 27
MINIPID 3PIN MANUAL Ion Science Ltd
Unrivalled Detection. www.ionscience.com
Parts List
MiniPID PPB PID: 1 ppb to 50 ppm range. Includes bulb and pellet.
MiniPID PPM PID: 0.1 ppm to 4000 ppm range. Includes bulb and pellet.
MniPID 10 eV PID: 5 ppb to 1 ppm range. Includes bulb and pellet.
LA4SM600 Replacement bulb. 10.6 eV only.
LA42SM60 Replacement 10.6 eV lamp and HPPM pellet for use with ppm MiniPID
A-846417 Replacement 10 eV pellet
BSF Replacement ppb pellet
846216 Extraction tool required for replacing bulb or pellet.
846217 Replacement spring.
A-31063 PID Lamp Cleaning Kit
Page 26 of 27
MINIPID 3PIN MANUAL Ion Science Ltd
Unrivalled Detection. www.ionscience.com
Version number
Update
Page
Date
V1.9
Manual reformatted throughout.
Factory lamp testing minimum voltage updated.
Log added
Page 10
Page 21
V2.0
Format and layout updated
All reference to PID changed to MiniPID
Page 8: STD inserted on line 3
Space added above MiniPID Reg
Non IS added to MiniPID Reg
Voltage on signal output added to IS table
‘line addition’ term for clarification only
Table version number update
Page 9: Duplication of Offset Voltage removed
Page 12: Word added ‘sensor is very much
unaffected’
300ms changed to 150ms
All of page 13 has been inserted from V1.6
Page 8
Page 9
Page 12
Page 13
20/05/2013
10/06/2013
10/06/2013
10/06/2013
10/06/2013
V2.1
Manual re-write to incorporate HPPM update
27/02/2014
Manual log
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