Ion Science MiniPID - Manual (Page 13)

MINIPID 3PIN MANUAL Ion Science Ltd
Page 13 of 27
Unrivalled Detection. www.ionscience.com
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 (V
s
- 0.1) V for the externally regulated voltage range of V
s
= 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:
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
*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.