Cooper Instruments & Systems DFI 1650 Multi-Channel Digital Force Indicator - Manual (Page 44)

CF 66 38 Rev. C 2/05
Step 4: Determine the LVDT’s electrical null point, then physically mount it. The electrical null is the armature
position that produces the least electrical output. Once this point has been determined, the transducer is physically
clamped into position. See “Electrical Null and Transducer Mounting” in Section 11.6.
Step 5: Perform the calibration.
Using the CALIBRATE menu item starts the calibration process. You will be prompted to apply displacements to
the transducer as required.
11.4 Specifications
TRANSDUCER INPUT
Transducer type Full-bridge, AC/AC-LVDT
Excitation voltage 3 VRMS @ 5kHz, short circuit protected
Transducer full-scale output .1 to 15 VRMS @ 3 VRMS excitation
Amplifier Gain Selection Automatic
Calibration Type 2-, 3- or 5-point known displacement
A/D Converter 24-bit Sigma-Delta
Low-pass filter Digital, 24-tap FIR
Resolution See section 11.5.1
Frequency Response See section 11.5.1
AUXILLIARY INPUTS
Quantity 2
Type Momentary contact closure
Response Time <5ms
Field-Selectable Functions Tare on, tare off, peak/valley clear, peak/valley hold, track hold
ANALOG OUTPUT
Voltage Range (voltage output channels) 5, ±5, 10 or ±10 VDC
Current Range (current output channels) 4-20 mA
Source Any channel’s track, peak or valley value
Isolation 500 V
Resolution 13 bits
Frequency Response Same as input if driven by the same channel’s tracking data
11.5 Channel Menu
Each AC/AC-LVDT Input channel is configured and calibrated via its channel menu. Detailed instructions on
operating the instrument in the SETUP Menu mode can be found in “SETUP Menu Mode”. A diagram of all menus
is located in “Setup Menu Reference” in Chapter 18.
11.5.1 OPERATION Sub-Menu
This menu controls the operation of this channel when the instrument is in the RUN mode.
AUTO-ZERO Menu Item
This enables or disables the channel’s automatic zeroing function. When enabled, the channel will reset its
tracking value to zero when the tracking value is less than 10 display counts for a period of 10 seconds. This
removes the effect of slight temperature shifts in the transducer’s output.
To compensate for the transducer’s initial warm-up shift, the auto-zero function operates every 2 seconds during
the first 60 seconds of RUN mode operation.
The two options for this menu item are “ON” and “OFF”.
FREQ.RESPONSE Menu Item
This sets the frequency response, step response, and resolution of the channel according to the table below. The
tracking value, peak/valley detector values and analog output on this channel are all affected. The default value of
016.HERTZ is suitable for most applications.