EPC
SERVO AMPLIFIER MODULE
Part Number L723888-3xx
ELECTRONIC
Telephone: (231) 929-1660
Oilgear
Fax:
(231) 929-7879
1424 International Dr
Issued May 31, 2018
Web Site:
www.oilgear.com
Traverse City, MI USA 4 9 6 8 6
Bulletin 836260F
43
4.4.5 LVDT Adjustment Algorithm
Both the HP Limiter and Stroke Controller portions of the Pump Controller module rely on the LVDT
being configured correctly. Typically, there are three (4) configuration parameters for each LVDT
(Refer to Section 4.4.2 for a complete overview):
•
Polarity
•
Offset
•
Course Gain
•
Fine Gain
The general sequence of operations for LVDT scaling is to
•
Set LVDT polarity to normal.
•
Place the EPC in Adjust mode.
•
Alternately Adjust the LVDT Offset and Gains until configured.
•
Return EPC to normal operation mode.
4.4.5.1. Determining LVDT Configuration Range
The LVDT input should be scaled to match the range of stroke command. The range of
stroke command is a factor of whether the pump is designed for uni- or bi-directional flow.
Servo valves are commanded with current: a positive current command will move the valve in one
direction while a negative current command will move the valve in the opposite direction. A neutral
(zero) current command will remove command to the valve: the valve might stay in its current
state, or it may move in either direction.
For a
uni-directional
pump, only one port is available and the stroke can supply 0 to 100% of
the rated flow. The LVDT should be configured so that the maximum positive toggle command
will produce the equivalent of a +10VDC command for the LVDT input. The maximum
negative toggle command should produce the equivalent of a 0 VDC command at the LVDT
input. The range of 0 to +10VDC corresponds to DAC values of 2048 to 4095, or a percentage
of 0 to +100% (refer to Section 5.1 for a discussion of the Diagnostic Representation of
Numbers).
For a uni-directional pump, the midpoint command is +5VDC (DAC value of 3072 or +50%
stroke).
For a
bi-directional
pump, two ports are available and the stroke can supply 0 to 100% of rated
flow in each direction. Like the uni-directional valve, the LVDT should be configured so that the
maximum positive toggle command will produce the equivalent of a +10VDC command for the
LVDT input. The maximum negative toggle command, however, should produce the equivalent
of a -10VDC command for the LVDT input. The range of -10VDC to
+10VDC corresponds to DAC values of 0 to 4095, or a percentage of -100% to +100% (refer to
Section 5.1 for a discussion of the Diagnostic Representation of Numbers).
For a bi-directional pump, the midpoint command is 0VDC (DAC value of 2048 or 0%
stroke).
