Model DT335-0700
Dual RTD/Resistance Input Transmitter w/USB
Acromag, Inc. Tel: 248-295-0880
- 27 -
http://www.acromag.com
- 27 -
https://www.acromag.com
How it Works...
Input 1/USB, Input 2, each output, and the power circuit are all isolated from each
other. The unit does not draw power from USB, but the USB port ground is
common to the input 1
circuit ground. The USB port ground of most PC’s is also
common to the USB cable shield and earth ground. Input 1 sensors could 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 1 ADC reference supply to ground and clipping its input
range.
TROUBLESHOOTING
Diagnostics Table
Before attempting repair or
replacement, be sure that all
installation and configuration
procedures have been followed
and that the unit is wired properly.
Verify that power is applied to the
unit and that your supply voltage is
at least 7V. Verify that your load is
appropriate to your output type,
current or voltage
If your problem still exists after
checking your wiring and reviewing
this information, or if other
evidence points to another
problem with the unit, an effective
and convenient fault diagnosis
method is to exchange the
questionable unit with a known
good unit.
Acromag’s Application Engineers
can provide further technical
assistance if required. Repair
services are also available from
Acromag.
POSSIBLE CAUSE
POSSIBLE FIX
Cannot Communicate with Unit
via USB…
Output shifts off-
range when you connect USB…
Output Erratic, Not operational, or at Wrong Value…
Unit fails to operate or exhibits an output shift…
A missing USB Isolator could
cause a ground loop between a
grounded input 1 sensor and
earth ground at the connected
Personal Computer’s USB port
because USB and input 1 share
a common ground connection.
Without USB isolation, a ground loop is
possible between a grounded input and earth
ground of the PC USB port. The input ADC of
the channel is normally ratiometrically biased
off input ground to process the input signal.
A grounded signal source could inadvertently
short this reference to earth ground and
prevent operation with a non-isolated USB
connection. For this reason and for increased
safety and noise immunity, it is best to
connect to USB via a USB isolator. Use an
isolator like the Acromag USB-ISOLATOR.
Otherwise, use a battery powered laptop to
configure the transmitter, which does not
normally earth ground its USB port.
Software Fails to Detect Transmitter…
Bad USB Connection
Recheck USB Cable Connection.
(Agility) Your smart device
needs permission to connect to
the Acromag transmitter the
first time.
When you first connect to your smart device,
it will prompt for permission. Be sure to give
your permission or Agility will not discern
your device connection. You may have to
unplug/replug the USB connection to your
tablet/phone to get this prompt.
USB has not enumerated the
device.
Use the reset button on the Acromag USB
isolator to trigger renumeration of the unit,
or simply unplug and re-plug the USB cable to
the transmitter.