ZERO AND GAIN ADJUSTMENT
• Locate header JP3 on UCM board. This determines the transducer gain settings.
• To establish the LVDT null point, set any jumper on header JP3 to the SET ZERO position, the other jumper may be removed or
placed in the LK2 position of header JP3. See Fig.6.
Fig 6 Fig 7 Fig 8
•Power up the UCM module. Rotate the ZERO trim pot until the output voltage reads the required mid stroke voltage (e.g.
2.500Vdc for a 0.5 to 4.5Vdc output). Remove the jumper on header JP3 from SET ZERO, the jumper can be placed in the LK1
position.
• Adjust LVDT core displacement until output signal reads 2.500Vdc (this is the LVDT null).
• Set the GAIN trim pot fully anticlockwise (this is a 20 turn pot).
• From null position displace the LVDT core to full-scale in the positive direction. Change the COARSE GAIN link settings in the
following order, leaving the links in the position that gives the nearest to (but not exceeding) the required full-scale output
(4.5V if no output option card is fitted on header JP7).
• Put one jumper in the DIV position and the other jumper in the K4 position of header JP3: See Fig.7.
Move the jumper from the K4 position to the K3 position.
Move the jumper from the K3 position to the K2 position.
Move the jumper from the K2 position to the K1 position.
Move both jumpers to the LK1 and LK2 positions: See Fig.8.
• Move one jumper to MULT and the other jumper to the K1 position See Fig.9
Move the jumper from the K1 position to the K2 position.
Move the jumper from the K2 position to the K3 position.
Move the jumper from the K3 position to the K4 position.
• Leaving the links in the position that gives the output nearest to (but not exceeding) the required output (4.5Vdc if no output
option card is fitted on header JP7), turn the GAIN trim pot until the required output is achieved (e.g. 4.500Vdc).
Note 1 Because the GAIN pot provides a small amount of overlap between coarse gain settings, it is sometimes possible to
calibrate an LVDT in either of two coarse gain settings. The above procedure ensures that the highest coarse gain
setting is always selected.
Note 2 If there are slight differences in the positive and negative sensitivity, or the displacements are different, then it may be
appropriate to set the zero to some other voltage within the output voltage range.
FITTING AN OUTPUT OPTION CARD
• Before fitting an option card, ensure that the ZERO AND GAIN ADJUSTMENT procedure has been completed, then power
down the UCM.
• Locate header JP7 on UCM board. (See Fig.1.)
Remove jumper from header JP7 (LK3).and place on header JP4 (See Fig.1.)
A choice of three output option cards is available:
VM – Voltage Module card to provide an extended range of voltage outputs.
CM – Current Module card to provide 4-20mA output.
PWM - Pulse Width Modulation card to provide a TTL level signal with 10-90% duty cycle.
Insert the selected option card on to header JP7 and follow the procedure for setting up each module card – see below.
• If the option card is no longer required, remove it and replace the jumper on header JP4 (LK4) to header JP7 (LK3).
SETTING THE VOLTAGE MODULE (VM) CARD
• When the Voltage Module (VM) output option card is selected, locate the DIP switch on VM card. (See Fig.10.) Select the
required output voltage, using the Switch Position Matrix Guide (Fig.11.), and set the DIP switch positions accordingly. Insert
connector of VM card onto the vacant pins of header JP7. Power up the UCM, monitor the voltage output and adjust the zero
and gain trim pots if necessary.
SET ZERO
LK1
LK2
MULT
Div
K1
K2
K3
K4
SET ZERO
LK1
LK2
MULT
DIV
K1
K2
K3
K4
SET ZERO
LK1
LK2
MULT
Div
K1
K2
K3
K4
Coarse
Gain Coarse
Gain
Coarse
Gain
JP3 JP3
JP3
JP3
MULT
Div
K1
K2
K3
K4
Fig 9
SET ZERO
LK1
LK2
