Oxford Instruments NanoScience MercuryiPS - Resistance Measurement in Constant Voltage Mode

Operator's Manual
MercuryiPS
©2016 Oxford Instruments
NanoScience
Rsensor = Rref x | ADCnorm
| x
Where:
Rref
is the reference resistance (either 2 kohms or 80 kohms).
ADCnorm
is the ADC reading, normalised to the range
RefGain
is the interpolated gain from the calibration tables.
ADCgain
is the gain setting of the ADC.
The measurement accuracy of this circuit does not depend on the accuracy of the excitation
current or the reference voltage. The accuracy prim
reference resistor plus any errors introduced by operational amplifiers.
11.3.3 Resistance
measurement
Constant voltage measurement mode is used with sensors that have a negative temperature
coefficient.
The sensor and a reference resistor (either R44 or R45) are connected in series. Digital to
analogue converters U24 and U25 generate an upper and lower demand voltage. The upper
voltage is buffered by U10 and applied to the upper end of the sensor res
Issue 14 /
Mar
NanoScience
. All rights reserved.
| x
RefGain / ADCgain
is the reference resistance (either 2 kohms or 80 kohms).
is the ADC reading, normalised to the range
0 to ±1 V.
is the interpolated gain from the calibration tables.
is the gain setting of the ADC.
The measurement accuracy of this circuit does not depend on the accuracy of the excitation
current or the reference voltage. The accuracy prim
arily depends on the accuracy of the
reference resistor plus any errors introduced by operational amplifiers.
measurement
in
constant voltage mode
Constant voltage measurement mode is used with sensors that have a negative temperature
The sensor and a reference resistor (either R44 or R45) are connected in series. Digital to
analogue converters U24 and U25 generate an upper and lower demand voltage. The upper
voltage is buffered by U10 and applied to the upper end of the sensor res
istor. The lower
Mar
2016
/ UMC0071
Page 129
The measurement accuracy of this circuit does not depend on the accuracy of the excitation
arily depends on the accuracy of the
constant voltage mode
Constant voltage measurement mode is used with sensors that have a negative temperature
The sensor and a reference resistor (either R44 or R45) are connected in series. Digital to
analogue converters U24 and U25 generate an upper and lower demand voltage. The upper
istor. The lower