VTI Instruments Ametek EX1200A Series, User Manual

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EX1200A Triggering 101
DMM Backplane
B
P
L
_
H
I
B
P
L
_
L
O
B
P
L
_
S
H
I
B
P
L
_
S
L
O
CH1_1
CH2_1
RTD
EX1200-3048
EX1200 Mainframe
.
.
.
F
IGURE
4-19: RTD 4-W
IRE
C
ONNECTION VIA THE
EX1200A DMM B
US
Programming Interface
The VTEX DMM and VTEX Scanner drivers provide the access to the features of EX1200A
DMM. Refer to the below functions of the driver in its documentation.
IVTEXDmmTemperature Interface
IIviDmmTemperature..::.RTD Property
Using a Thermistor
While RTDs can be used over a wide temperature range, thermistors offer a higher sensitivity to
temperature change, although they must operate in a more restricted temperature range.
Thermistors are resistance-based passive transducers whose output resistance varies with
temperature changes. By measuring the resistance of the thermistor, the temperature can be
derived. The following thermistors are predefined on the EX1200A DMM and use built-in
software conversions: 2.252
kΩ (default), 5 kΩ, and 10 kΩ.
Custom thermistors can be defined by providing the appropriate variables in the Steinhart-Hart
equation:
A , B , and C
(refer to the thermistor manufacturer’s data sheet for more information). The
equation is as follows:
   
 
3
ln ln
1
R C R B A
T
K
 

Where: T
K
= calculated temperature in Kelvin
ln (R) = natural log of measured resistance value of thermistor
T = temperature in °C
A, B, C = curve-fitting constants