GPI GM001, Руководство пользователя, Страница: 11 / 20

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Setting the Low (4 mA) Endpoint:
To set 4 mA at zero flow, go to step 3. Otherwise follow
steps 1, 2 and 3:
1. Start the fluid pumping system. Set it for steady flow at
the lowest anticipated rate (or the rate at which you want
a “minimum” indication).
2. Wait while the fluid flow is uninterrupted for at least 10
seconds.
3. While watching the transmitter’s indicating light, press
and hold both its “SET” and “4” buttons. Release them
when the light blinks.
NOTE: The length of time between “button press” and “light
blink” depends on the transmitter response time. The
maximum is 5.2 seconds. If you can’t see the indicator
light (if you’re outdoors in bright light), you can safely just
count to 10 while holding the pushbuttons.
NOTE: After setting the minimum, the loop current should be
registering at or near 4 mA. Don’t worry if it’s not exact, it
will be correct after setting the high (20 mA) endpoint.
Setting the High (20 mA) Endpoint
1. Start the fluid pumping system. Set it for steady flow at
the highest anticipated rate (or the rate at which you want
a “maximum” indication).
2. Wait while the fluid flow is uninterrupted for at least 10
seconds.
NOTE: If you observe the current loop after completing the
procedure, it should be registering at or very near 20
mA (within the resolution specifications for the present
conditions).
3. While watching the transmitter’s indicating light, press
and hold both its “SET” and “20” buttons. Release them
when the light blinks.
NOTE: During the high and low setpoint procedure, if the new
settings are very different from the previous settings, it is
possible to reverse the 4 mA and 20 mA setpoints so that
the 4 mA frequency is
higher
than the 20 mA frequency.
The situation corrects itself after you complete both
setpoints. If the new settings are close to the previous
settings, you may safely set either the low and high set-
tings independently.
Lockout Feature
This transmitter includes a user selectable lockout feature.
Select the feature after setting the 4 and 20 mA endpoints
during initial use. The lockout feature prevents tampering with
the 4 and 20 mA settings on the transmitter.
Before activating the lockout feature make sure there is no
signal being received by the transmitter. If signal is being
received, deactivate it by one of the following methods:
• Stop the flow through the line that is being recorded.
• Disconnect the output device on the flowmeter.
Locking / Unlocking the Transmitter
Position yourself so you can easily operate the pushbuttons on
the transmitter. You should be able to see the indicator light.
To
lock
the transmitter, use the pushbuttons to enter the
following sequence with a brief pause between each button
press: 20 – 20 – 20 – SET. The indicator light will blink twice
to indicate the unit is locked.
To
unlock
the transmitter, use the pushbuttons to enter the
following sequence with a brief pause between each button
press: 4 – 4 – 4 – SET. The indicator light will blink once to
indicate the unit is unlocked.
Checking the Status of the Lockout Feature
To check the status of the transmitter, use the pushbuttons
to enter the following sequence with a brief pause between
each button press: SET – 4 – 20 – SET. The indicator light
will blink once if unlocked or twice if locked.
Optional 0-20 mA Mode
A few current loop systems use 0-20 mA output. The input
signal frequency of “0” produces an output analog signal of
“0” with direct proportionality and no offset.
NOTE: A true loop current of “0” in a loop powered device
like the GPI transmitter is not obtainable. That’s because
the current loop powers the transmitter, and its operat-
ing current is non-zero even at zero frequency input. In
0-20 mode, the GPI Transmitter’s loop current will drop
to as near zero as possible at zero input, in most units
between 1 and 2 mA.
Procedure
1. To enter 0-20 mode, simply press and hold all three push-
buttons simultaneously (4, SET, and 20) at any flowrate.
Continue holding until the indicator light blinks (light will
blink in up to 5 seconds) and release all buttons. This
sets the LOW END calibration point to zero/zero.
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 4).