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Setup Menu T400 Ozone Analyzer Operator’s Manual
118
5.10.1.5. Manual Adjustment of Current Loop Output Span and Offset
A current loop option may be purchased for the A1 and A2 Analog outputs of the
analyzer. This option places circuitry in series with the output of the D-to A converter
on the motherboard that changes the normal DC voltage output to a 0-20 milliamp
signal. The outputs can be ordered scaled to any set of limits within that 0-20 mA range,
however most current loop applications call for either 0-20 mA or 4-20mA range spans.
All current loop outputs have a + 5% over range. Ranges whose lower limit is set above
1 mA also have a –5 under range.
To switch an analog output from voltage to current loop, follow the instructions in
Section 5.10.1.6 and select CURR from
the list of options on the “Output Range” menu.
Adjusting the signal zero and span levels of the current loop output is done by raising or
lowering the voltage output of the D-to-A converter circuitry on the analyzer’s
motherboard. This raises or lowers the signal level produced by the Current Loop
Option circuitry.
The software allows this adjustment to be made in 100, 10 or 1 count increments. Since
the exact amount by which the current signal is changed per D-to-A count varies from
output-to-output and instrument–to–instrument, you will need to measure the change in
the signal levels with a separate, current meter placed in series with the output circuit.
See Figure 3-7 for pin assignments and diagram of the analog output connector.
Figure 5-5: Setup for Checking Current Output Signal Levels
CAUTION – General Safety Hazard
DO NOT EXCEED 60 V PEAK VOLTAGE BETWEEN CURRENT LOOP OUTPUTS
AND INSTRUMENT GROUND.
06870C DCN6332