TReX User Manual v2.14 Firmware
DAC CAL Sub-Menu
Analog outputs can be configured to operate as constant voltage or constant current. This
makes the outputs suitable for outputs such as 0-10V or 4-20mA.
The analog output is current limited internally at approx 35mA. DAC Output impedance is 5
ohms.
In VOLTAGE mode:
Ensure that the wiring SERIES impedance is as low as possible. There will be a voltage drop
across any series resistance that will affect the output voltage. How much the output will vary
will depend on the load of the connected equipment. This load resistance preferably should
not be less than 2k ohms.
In CURRENT mode:
Ensure that the full loop impedance is less than 500 ohms and at least 100 ohms. Add a small
series resistor if required since the internal series resistance is only 5 ohms.
When the analog outputs are being controlled, scaling can be applied that allows the user to
specify an OUTPUT from 0-1023 over a useful range from MIN to MAX. For example, if
MIN is 200 and MAX is 400, then setting the analog output to a SET value of 1023 will in fact
set the OUTPUT to the MAX value of 400. SET configured to 0 will set the OUTPUT to the
MIN value of 200. A SET value of 512 will set the OUTPUT to a value of 300. See following
calibration procedure for full example.
MIN
This is the minimum used unscaled DAC count of interest. If no scaling is to be applied set to
0.
MAX
This is the maximum used unscaled DAC count of interest. If no scaling is to be applied set to
1023.
SET
This sets the output as a value between 0-1023 that is scaled and applied between the MIN and
© WTE Limited, 2018 – Christchurch New Zealand
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