Ion Science MiniPID - Manual (Page 12)

MINIPID 3PIN MANUAL Ion Science Ltd
Page 12 of 27
Unrivalled Detection. www.ionscience.com
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: V
s
= 3.6 to 18.0 V, V
s
= 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.
Soldered
Unsoldered
(intrinsically safe
environment)
Unsoldered
(Non-intrinsically
safe environment)
MiniPID PPM, V
s
3 to 3.6 V 3.6 to 10 V 3.6 to 18V
MiniPID PPB, V
s
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)