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ROC827 Instruction Manual
Issued Mar-06 Troubleshooting 6-6
Caution
Failure to exercise proper electrostatic discharge precautions, such as
wearing a grounded wrist strap may reset the processor or damage
electronic components, resulting in interrupted operations.
1. Connect a multimeter across the scaling resistor connected to the +
and COM terminals of the module and set the multimeter to measure
voltage.
2. Connect to ROCLINK 800 software.
3. Select Configuration > I/O > AI Points.
4. Select the correct Analog Input Point Number.
5. Verify the following readings:
When the Value is –25% of span as configured in Table 6-1, it is
an indication of no current flow (0 mA), which can result from
open field wiring or a faulty field device. The multimeter should
show 0 (zero) Volts dc.
When the Value is in excess of 100% of span as configured in
Table 6-1, it is an indication of maximum current flow, which can
result from shorted field wiring or a faulty field device. The
multimeter should show 5 Volts dc.
When the Value is between the Low Reading EU and the High
Reading EU, verify the accuracy of the reading by measuring the
voltage across the terminals with the multimeter.
6. Convert this reading to the Value value:
Value = [((V
multimeter
– 1) ÷ 4)
*
Span] + Low Reading EU
where Span = High Reading EU – Low Reading EU.
Note: This calculated value should be within one-tenth of one percent
of the Filter value measured by the ROC827.
7. Verify the accuracy by reading the loop current with a multimeter,
setting the multimeter to measure current in mA, and connecting it in
series with current loop. Be sure to take into account that input values
can change rapidly, which can cause a greater error between the
measured value and the calculated value.
8. Calculate the Value from the mAmp reading of the multimeter:
Value = [((mAmpmultimeter* Rscaling resistor – 1) * 4) * Span] + Low
Reading EU
where Span = High Reading EU – Low Reading EU and Rscaling
resistor should be 250 ohms (factory installed scaling resistor value).
Note: If the calculated value and the measured value are the same, the
AI module is operating correctly.