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2. Set the 20 mA endpoint as described above under 4-20
mA calibration.
3. The special 0-20 mode will remain in effect until a new
4 mA endpoint is established in the usual way.
Auxiliary 0-5 VDC
The 4-20 mA Out with Display is equipped with an auxiliary
voltage output with a range of 0-5 VDC. This signal is capable
of dropping to within a few milliVolts of zero, and thus may be
more suitable for use in the 0-20 mode.
No special equipment is required to use the 0-5V output, but
wiring to customer equipment is different (see Wiring Diagram 3).
Changing Response Time
The 4-20 mA with Display comes from the factory with a default
0.7 seconds response time.
WARNING
If you reset the response time (procedure detailed below)
you MUST then reset the 4-20 mA endpoints.
To give good performance with a variety of sensor types, many
frequency-to-analog converters, including the GPI 4-20 mA
Out with Display, offer two or more settings for "response time"
(sometimes referred to as "settling time" or "averaging time").
• Longer (slower) response times are needed for sensor types
that generate very low frequency outputs.
• Operating a meter at high flowrates may require a shorter
(faster) response time to achieve the best transmitter perfor-
mance.
• Shorter (faster) response times are preferable for sensors that
generate higher frequency outputs (GPI TM Series Meters,
for example).
• Longer (slower) response times are also appropriate in situ-
ations where sensor-output frequency fluctuates or wobbles
substantially.
The GPI 4-20 mA Out with Display offers a choice of five
response-time settings, selectable by the unit's pushbuttons.
Procedure
1. Start with the unit unpowered. If the unit is presently operat-
ing, temporarily disable its external power supply. Be sure
to allow at least 30 seconds to elapse with unit unpowered.
2. Press and hold the "4" button. While holding, watch the
indicator light and power up the 4-20 mA Out with Display.
3. Shortly after power is applied, the light will blink one or more
times. Count the number of blinks (from 1 to 5 blinks) and
release the button after the blinking has finished.
NOTE: If necessary, repeat steps 1 through 3 to get the number
of blinks corresponding to the response time you want.
Blinks
Response Time
1 blink
0.3 second
2 blinks
0.7 second
3 blinks
1.3 second
4 blinks
2.6 second
5 blinks
5.2 second
In normal operation, the 4-20 mA Out with Display always av-
erages two sequential input readings. The time delay from an
abrupt change in input frequency to a final, stabilized output
reading is always twice that shown in the above table.
MAINTENANCE
Check cable-entry seals periodically. Tighten and/or apply seal-
ant if needed. This is especially important in environments con-
taining heavy concentrations of dust, oil mist or other residue.
Check all wiring connections occasionally for oxidation or cor-
rosion. Clean and re-seat if such conditions are noted.
If necessary, check and re-seat any connections that may have
been subjected to strain (during rework or construction, for
example).
15
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