Operator's Manual
Issue 14
/
Mar 2016 / UMC0071
Mercury
iPS
©2016 Oxford Instruments NanoScience. All rights reserved.
Page
137
13 PRESSURE BOARD
This board provides isolated, precision pressure measurements from a pressure transducer.
The pressure board can interface with 3 types of pressure transducer:
1 Absolute Current Output (eg. Omega
PX309-015AI)
2 wire
2 Absolute Voltage Output (eg. Omega
PX309-015A5V
) 3 wire
3 Ratiometric Voltage Output (eg. Omega
PX309-015AV
) 4 wire.
13.1 Description of the pressure board
The pressure card provides 10 volt or 15 volt on-board excitation for voltage output transducers
and up to 25mA at up to 15volts for absolute current output transducers. The absolute voltage
and absolute current transducers may also be energised from an external supply but this is not
supported for ratiometric voltage transducers.
4-20mA current and 0-10 volt transducer outputs are measured on an auto-ranging 24 bit sigma
delta ADC with a 0.04% accurate voltage reference. Together with other high precision
components and automatic self-calibrating, this results in high accuracy and stability and low
noise measurements.
The pressure sensor input is via 9-way D-connector on the rear panel of the iPS. A filtered 80
watt heater is available on this connector when the board is fitted in slot 6, 7 or 8, with a
corresponding heater board in slot 1, 2 or 3.
Extensive power-on diagnostics and continuous circuit monitoring assure the user that circuits
are fully functional, operating correctly and that sensors remain properly connected. All external
pins are diode protected to the power rails and current limiting resistors are fitted to the
excitation supply as protection against short circuits.
13.1.1 Description of the pressure board circuit
A block diagram of the pressure board is given below.
