Red Lion PAXLCL - Manual (Page 8)

Example 1:
A PAXLCL is to be calibrated to match a flow transducer whose output is 10
mA @ 0 GPM and 50 mA @ 1375 GPM.
READOUT SPAN (Rs) = 1375
 0 = 1375
SWING CURRENT (Is) = 50 mA  10 mA = 40 mA
ADJUSTMENTS (Refer to the transfer curve below)
 Null the unit to zero readout @ 0
current per Steps 1 to 4 of the
calibration steps.
 Set the coarse and fine span adjustments
to get a readout of 1375 @ 40 mA per
Steps 5 and 6. Note: With the full
standard swing of 40 mA, the coarse
span switch reference markings can be
used to determine settings as follows:
S7 ON (1050) + S9 ON (260) = 1310
Span set with switches.
375 (needed) - 1310 (with SW’s) = 65
w. fine span adj.
 Set offset to readout 0 @ 10 mA per Step 7. Note: The read out observed
when the 10 mA min. current is first applied can be used to determine the
offset switch settings.) In this example the readout will be (+) 344 when the
10 mA min. current is first applied. Applying -344 offset then reduces the
readout to zero @ 10 mA.
 Check readout at max. (50 mA) and min. (10 mA) and fine tune (tweak) as
required per Step 8.
Example 2 (Negative Slope):
A level measuring device puts out 6 mA when a storage tank is full and 15
mA when the tank is empty. The PAXLCL is to readout 90.0 tons at full tank
and zero when empty.
READOUT SPAN (Rs) = 900  0 = 900 (Disregard Decimal Points)
SWING CURRENT (Is) = 6 mA (@ max rdg) - 15 mA (@ min rdg) = -9 mA
In this case, the signal current is reverse [Term 3 (-) with respect to Term 5
(+)] causing the readout to go “down” (increasingly negative) as the negative
current increases.
ADJUSTMENTS
 Null the unit per Steps 1 to 4.
 Set slope of transfer curve with span
adjustments to get readout of -900
@ -9 mA per Steps 5 and 6.
 Move transfer curve up by applying
(+) offset per Step 7 until readout is
+900 @ -6 mA.
 Check extreme readings per Step 8,
0 readout @ -15 mA and +900
readout @ -6 mA. Set D.P. Switch
S1 and replace unit in case.
Example 3 (± Display):
A differential pressure transducer has a range of ±1500 PSI with a 4 to 20 mA
output (-1500 @ 4 mA, +1500 @ 20 mA).
READOUT SPAN (Rs) = +1500
(1500) = 3000
SWING CURRENT (Is) = 20 mA(max) - 4 mA(min) = 16 mA
Note: Since the display readout is limited to 1999 numerical indication, the
full READOUT SPAN of 3000 cannot be obtained during zero based span
adjustment. However, dividing both the READOUT SPAN and SWING
CURRENT by two, i.e. 1500 readout @ 8 mA, allows the span adjustment
to be made for the proper transfer curve slope.
ADJUSTMENTS
 Null the unit per Steps 1 to 4.
 Set transfer curve slope with span
adjustments per Steps 5 and 6, to get
a readout of +1500 @ 8 mA.
 Apply (-) offset per Step 7 to get a
reading of -1500 @ 4 mA.
 Check min. and max. extremes and
tweak if required to get desired
readout @ 4 and 20 mA per Step 8.
1375
OFFSET
READOUT
NULL
40
B SPAN
10 50 MA MA MA
CURRENT
D
CHECK
C
A
6.0 A
PPLICATIONS
C
A
D
CHECK
READOUT
B
CURRENT
(+) (-)
-15
MA
-9
MA -6
MA
-900
+900
OFFSET
NULL
SPAN
SPAN
OFFSET
CURRENT
(-)
4
MA
B
8
MA
20
MA
-1500
NULL
A
(+)
C
READOUT
+1500
D
CHECK
CHECK D
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