Teledyne GFC 7001E User Manual download pdf (Page 139)

Advanced Features Model GFC7001E Carbon Dioxide Analyzer

Teledyne Analytical Instruments 139

7.4.3.5. Manual Adjustment of Current Loop Output Span and Offset

A current loop option may be purchased for the A1, A2 and A3 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 (see Section 5.4).

 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 4-20 mA 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 7.4.2 (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 7-6: Setup for Checking / Calibration Current Output Signal Levels Using an Ammeter

CAUTION

GENERAL SAFETY HAZARD

Do not exceed 60 V peak voltage between current loop outputs and instrument

ground.

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Teledyne GFC 7001E User Manual Page 139