Seametrics AO45 - Manual (Page 3)

Field Calibration. Ordinarily the AO45 is ordered with
a flow sensor or meter and is factory calibrated to a re-
quested flow range. However, the unit can be field-cali-
brated if necessary. A frequency generator and a multi-
meter are required. Follow these steps:
1. Calculate 20 mA frequency. Determine the flow rate
at which 20 mA output is desired. Determine the K-fac-
tor (pulses per gallon) of the flow sensor. For SeaMet-
rics units, this is marked on the sensor. Use this for-
mula:
Frequency =
2. Select range. There are two frequency ranges, 10 -
100 pulses per second and 100 - 1,000 pulses per sec-
ond. Note the range into which the calculated 20 mA
frequency falls.
Find the frequency jumper. Choose position HI or LO
and place the jumper there.
4-20mA
Output -
-
+
+
4mA
adjust 20mA
adjust
HI LO
FREQ.
-
+
Multimeter set
to read mA
Power Source
(12 - 36 VDC)
Select range here:
Lo 20 mA = 10 - 100 Hz
Hi 20 mA = 100 - 1000 Hz
Signal
Generator
5V Min.
signal
- +
mA
Field Calibration
3 of 4
K-factor(PPG) X Flow Rate(GPM)
60
3. Connect multimeter. Set the multimeter for mA and
connect to the 4-20 mA terminals, observing polarity.
Apply power.
4. Adjust 4 mA. Locate the trimpot marked “4 ADJ”. Dial
the pot until your multimeter reads 4.00 mA.
5. Connect frequency. Set your frequency generator for
the 20 mA frequency as calculated above. Connect to
the input terminals marked “SENSOR” and + 12 V.
6. Adjust 20 mA. Dial the trimpot marked “20 ADJ” until
your multimeter reads 20.00 mA. Disconnect the multi-
meter. Calibration is completed.
DIS
CON
TIN
UED