Cooper Instruments & Systems DFI 1650 Multi-Channel Digital Force Indicator - Manual (Page 35)

CF 66 29 Rev. C 2/05
Calibration transducers
Max. distance of transducer from
instrument w/out sense wires 15’ [5m] 50’ [15m] 300’ [100m]
Max. distance of transducer from
instrument with sense wires 15’ [5m] 100’ [30m] 300’ [100m]
CALIBRATION TECHNIQUE
Zero-scale point from… Applied load Applied load Applied load
Full-scale point from… Transducer output when
shunt resistor applied
Internal reference Applied load
Linearity correction from… data stored in Signature
Module (if available)
Data stored in
Signature Module (if
available)
2-point: none
3- or 5-point: applied load
It is important to know your application
in order to select the appropriate calibration type. mV/V (“millivolts-per-
volt”) Calibration is recommended for most applications because it doesn’t require known loads and it allows easy
swapping of transducers equipped with Signature Calibration. When the best possible accuracy is required, Know-
Load Calibration is recommended.
The choices for this menu item are:
• “TYPE=SHUNT CAL” means Shunt Calibration. First, you are prompted to apply the load entered in the
“ZERO SCALE VALUE” register. Next, the instrument inserts a known, precision resistor into the transducer
circuit, which causes a predictable apparent signal. The instrument then takes a reading and adjusts itself
using the “SHUNT CAL VALUE” register.
• “TYPE=MV/V CAL” means Millivolt-per-Volt Calibration. First, yoare prompted to apply the load entered in the
“ZERO SCALE VALUE” register. Next, the instrument takes a reading from an accurate, internal mV/V
reference. The instrument then uses the “FULL SCALE MV/V” and “FULL SCALE VALUE” values in
mathematical calculations to scale its tracking values.
• “TYPE= 2 POINT CAL” means 2-Point Known Load Calibration. You are prompted to apply the loads to the
transducer that were entered in the “KNOWN POINT ½” and “KNOWN POINT 2/2” registers. This technique
assumes that the transducer is linear, so the usual loads are zero scale and full scale.
• “TYPE=3 POINT CAL” means 3-Point Known Load Calibration. You are prompted to apply the loads to the
transducer that were entered in the “KNOWN POINT 1/3” and “KNOWN POINT 2/3” and “KNOWN POINT 3/3”
registers. This technique can be used to compensate for the non-linearity in the transducer. The usual loads
used are zero scale, half scale and full scale, but you are not restricted to these loads.
• “TYPE=5 POINT CAL” means 5-Point Known Load Calibration. You are prompted to apply the loads to the
transducer that were entered in the “KNOWN POINT 1/5”, “KNOWN POINT 2/5”, “KNOWN POINT 3/5”,
“KNOWN POINT 4/5” and “KNOWN POINT 5/5” registers. This technique can be used to compensate for the
non-linearity in the transducer. The usual loads used are zero scale, on-quarter scale, half scale, three-
quarters scale and full scale, but you are not restricted to these loads.
The selection of the calibration type affects what menu items appear in the CALIBRATION DATA sub-menu.
10.5.5 CALIBRATION DATA Sub-Menu
This enters the values that will be used by the instrument when it calibrates itself to the transducer. The menu
items that are displayed will change according to what the CALIBRATION TYPE is set for.
EXCITATION Menu Item
This sets the excitation voltage used to power up the transducer. The choices are:
• “EXCITATION=5VDC” means 5 volts DC excitation
• “EXCITATION=10VDC” means 10 volts DC excitation.
This menu item may be automatically updated by a transducer’s Signature Module.
FULL-SCALE MV/V Menu Item
The transducer output when its full-scale load is applied to it, in milliVolts-per-Volt. This menu item is used by the
instrument to set the gain of its amplifier circuit, and (when the CALIBRATION TYPE is set to mV/V Calibration) to
calibrate the instrument. This value is normally found on the transducer’s Certificate of Calibration issued by its
manufacturer.