GPI GM Serie Guía De Operación página 12

The 4-20 mA Out with Display is equipped with an auxil-
iary 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 out-
put, but wiring to customer equipment is different (see
Wiring Diagram 4).
Changing Response Time
The 4-20 mA with Display comes from the factory with
a default 0.7 seconds response time.
If you reset the response time (procedure detailed
WARNING
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 sen-
sor types that generate very low frequency outputs
(like GM Series oval gear flowmeters).
• Operating a meter at high flowrates may require a
shorter (faster) response time to achieve the best
transmitter performance.
• Shorter (faster) response times are preferable for
sensors that generate higher frequency outputs (GPI
turbine meters, for example).
• Longer (slower) response times are also appropriate
in situations where sensor-output frequency fluctu-
ates 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
operating, 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
12
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 al-
ways averages 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.
Check cable-entry seals periodically. Tighten and/or
apply sealant if needed. This is especially important in
MAINTENANCE
environments containing heavy concentrations of dust,
oil mist, or other residue.
Check all wiring connections occasionally for oxidation
or corrosion. 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).