UM-0085-B09
DT80 Range User Manual
Page 320
RG
Calibration
The channel factor (shunt resistor value) can also be used as a calibration factor. For example, if the sensor reads
290.7K when the actual temperature is 289.5K (an error of +1.2K) then the required scaling factor would be 1 – (1.2 /
289.5) = 0.9959, which would then be multiplied by the nominal shunt resistance (100). So the correction would be
applied as:
1AD590(99.59)
Note:
if the DT80's internal shunt is used (e.g.
1#AD590
), then you need to specify the shunt resistor's nominal resistance as the
channel factor when doing the calibration measurement, i.e.
1#AD590(100)
. If this is not done then the DT80 will use the actual
shunt resistance (which it determines during its self calibration process), which will upset the above calculation because you won't know
what to multiply the scaling factor by.
IC1 – 2-Wire AD590-Series Inputs
The wiring configuration shown below uses the DT80's internal voltage excitation to power the sensor, and the internal
shunt resistor to measure the output current.
Figure 146: Wiring for AD590 series input using internal shunt
To measure
Use the command
temperature
1#AD590
Other Wiring Options
External shunts and/or external power supplies (as per the wiring configurations for current) can also be used to allow
more sensors to be measured per channel. The Series 4 models provides built-in 16-bit DAC converter at V/I DAC
terminal. It capable to generate voltages up to 10V with current 25mA max. The DAC output can be used as an external
excitation power source and connected to
EXT*
terminal .
For example, the configuration shown in
C1 – Shared Terminal Current Inputs using External Shunts (P306
) could be
used to allow three AD590s to be measured on the one channel. Note that in this case the N channel option would be
required, in order to disable the default voltage excitation output on the * terminal, i.e.
To measure temperature
Use the command
I1
1*AD590(N,
R1
)
I2
1+AD590(N,
R2
)
I3
1-AD590(N,
R3
)
Alternatively, separately connected shunts could be used, as shown in
C2 – Independent Current Inputs using External
. That is:
To measure temperature
Use the command
I1
1AD590(N,
R1
)
I2
1*AD590(N,
R2
)
