Liquid Controls SP720-2 - Manual (Page 3)

Sponsler, Inc. SP720-2 Transmitter pg 3 DOC# MN-720
BENCH TEST CALIBRATION PROCEDURE
Required Equipment: Power Supply 5-28 VDC, Digital Multimeter (DMM), Frequency
Generator, Frequency Counter, Oscilloscope
Test Procedure:
A) Connect DMM positive lead to power supply positive and the DMM negative
lead to J1-3, Set DMM function to mA DC
B) Connect power supply negative lead to J1-5
C) Connect RF pickup coil to J1-1, 2
D) Connect oscilloscope positive and negative leads to J1-1, 2 respectively
E) Set S1 for desired full scale frequency range
F) Turn power supply ‘ON’. Observe oscilloscope displays 50KHz
± 5KHz 6Vp-p
carrier sinewave
G) Adjust ‘ZERO’ (R25) for 4.00mA DMM indication
H) Disconnect oscilloscope @ J1-1,2. Connect frequency generator positive and
negative leads to J1-1,2 respectively, set function to squarewave and
amplitude to 5Vp-p (0-5v) and frequency to the desired full scale point
I) Adjust ‘SPAN’ (R20) for 20.00mA DMM indication
J) Reduce signal amplitude to frequency generator to zero, adjust ‘ZERO’ (R25)
for 4.00mA DMM indication if necessary
K) Adjust signal amplitude of frequency generator to 5Vp-p, adjust ‘SPAN’ (R20)
for 20.00mA DMM indication if necessary
L) Adjust frequency of frequency generator to exactly 50% of the maximum
frequency point in step H, DMM should indicate 12.00mA
±.06, repeat 25%,
75% points
To check for linearity @ any frequency point incorporate the following formula-
(F/F max X 16) + 4 = mA
Example: Assume maximum frequency point = 2000Hz (20.00mA point)
Check for linearity @ 750Hz point
750/2000 = .375
16 X .375 = 6
6 + 4 = 10 DMM should indicate 10.00mA @ 750Hz input