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current monitoring

current ue9 sensor transducer

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#1 Aro

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Posted 18 September 2014 - 12:40 PM

I'm trying to monitor the status of a heater to determine if/when it burns out.  I am using a UE9 to control a DC relay that sends 36V to a heater (essentially just coiled resistance wire) that will draw ~2A.  The application is such that burn outs or shorts are common, but I need to know when they happen.  I'm new to LabJack and electrical engineering in general and I don't know the best way to go about this.  I would think that monitoring the current and looking for a large deviation from the expected value would be the easiest.  Is there another way of doing this, and what kind of current transducer should I be looking for?

#2 LabJack Support

LabJack Support
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Posted 18 September 2014 - 12:48 PM

Monitoring the current sounds like a good idea.  Here is some information we have provided before about finding a current sensor:


For current, you need a current sensor.  I suggest a hall-effect
sensor.  A hall-effect sensor is isolated so you don't have to worry
about grounding or common-mode voltage issues.  You simply connect
VS/GND to the sensor to provide it power, and then connect the signal
wire to an analog input.

When I am looking for Hall Effect sensors  I start here at Digikey:

http://www.<span sty...66573?k=current

First I go to the "Voltage - Supply" column and ctrl-select all ranges
that include 5.0V, then click "Apply Filters".  Then I go to the
"Current - Sensing" column and ctrl-select ranges that might work.  You
also might check the "In stock" box.  That usually leaves me with about
1 page of results.

When you select which ranges you want in the "Current - Sensing"
column, it is not always straightforward.  For example, if the max
current you want to measure is 10 amps, that does not necessarily mean
you should select a sensor rated for exactly 10 amps.  You have to

    - The signal output voltage of the sensor at different currents.
    - The signal input range of the LabJack.

For example, consider the SCD10PUN.  Following are its signal output
at different currents:

0A        0.3V
10A      2.3V
20A      4.3V

The U3-HV, U6, UE9, and T7, all have analog inputs that can measure up
to 5 or 10 volts, so the SCD10PUN is good for measuring up to 20 amps
with those devices.  The analog inputs on the U3-LV have an input
range of 0-2.4 or 0-3.6 volts, so it is good for 0-10.5 or 0-16.5 amps
with the SCD10PUN.

Also tagged with one or more of these keywords: current, ue9, sensor, transducer

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