Teledyne T300, Руководство по эксплуатации, Страница: 132 / 426

Setup Menu Teledyne API – Model T300/T300M CO Analyzer
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5.9.3.7. 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 3.3.1.4).
•
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 5.9.3.1 (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 3-9 for pin assignments and diagram of the analog output connector.
mADC
IN OUT
Recording
Device
I IN +
I
IN -
ANALYZER
I OUT +
I
OUT -
Ammeter
Figure 5-5: Setup for Checking / Calibration Current Output Signal Levels Using an Ammeter
CAUTION
G
ENERAL
S
AFETY
H
AZARD
Do not exceed 60 V peak voltage between current loop outputs and instrument ground.
06864B DCN6314