Model DT333-0700
4-Wire mV/TC Dual Transmitter w/USB
Acromag, Inc. Tel: 248-295-0880
- 25 -
http://www.acromag.com
- 25 -
https://www.acromag.com
BLOCK DIAGRAM
How It Works
Key Points of Operation
-
Unit is DC powered and power is
Isolated.
- Input is Differential
- Dual Isolated Output Channels
with both current and voltage
output terminals.
- Input circuit ground is common
to USB ground.
This transmitter uses a 32-bit microcontroller and two high-resolution 24-bit A/D
’s
to digitize the input signals and communicate to each output DAC via a digitally
isolated SPI bus. The input signals are transmitted to 16-bit output DACs which
each drive separate voltage and current terminals that share an output return.
Power for the isolated input and isolated output circuits is provided via an isolated
fly-back converter that operates on voltage wired to the power terminals at TB5,
and/or to optional bus power terminals along the DIN rail. Set up involves selecting
the input range for each input (T/C type or ±100mV/±1V), selecting the output
range for each output (current or voltage), selecting input filter levels, and scaling
input range endpoints to each output range zero/full-scale endpoints. I/O scaling
may be done in reverse to produce a reverse acting output signal. Refer to the
block diagram above to gain a better understanding of transmitter operation.
The input1/USB, input 2, each output, and power circuits are isolated from each
other. The USB port ground is common to the input 1 circuit ground. This unit does
not draw power from USB. T
he USB port ground of most PC’s is common to the USB
cable shield and earth ground and input sensors may additionally be grounded or
ungrounded. For this reason, it is recommended that USB signals be isolated when
connected to a PC to prevent a ground loop from occurring between the PC earth
ground and a grounded input 1 sensor, which would have the negative effect of
pulling the input bias supply to ground and clipping any negative range.
