2308-900-01 Rev. A / July 2008
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Section Topics
13-3
Model 2308 Portable Device Battery/Charger Simulator User’s Manual
Section 13: Calibration
Calibration cycle
Perform calibration at least once every two years to ensure the unit meets or exceeds its
specifications.
Recommended calibration equipment
Table 13-1
lists the recommended equipment for the calibration procedures. You can use alternate
equipment as long as that equipment has specifications at least four times better than
corresponding Model 2308 specifications. See also
Resistor considerations
later in this section for
important temperature coefficient information.
Resistor connections
When performing calibration steps that use either the 4
Ω
or 3k
Ω
resistor, connect the Model 2308
OUTPUT #1 or OUTPUT #2 SENSE leads and Model 2001 DMM test leads as close to the
resistor body as possible.
Resistor considerations
The test resistors should be characterized using the 4-wire ohms function of the DMM
recommended in
Table 13-1
to measure the resistance values. Use the measured resistance
values to calculate the actual currents during the calibration procedures.
Table 13-1
Recommended calibration equipment
Description
Manufacturer/
Model
Specifications
Digital Multimeter
Keithley 2001
DC Voltage
*
20 V: ±22 ppm
2 V ± 20 ppm
Resistance
*
20
Ω
: ±59 ppm
20k
Ω
: ±36 ppm
Precision Resistor
4
Ω
, 0.1%, 100 W
**
Precision Resistor
3 k
Ω
, 0.1%, 0.125 W
**
*
Full-range, 90-day, 23°C ±5°C accuracy specifications of ranges required for various measurement
points.
**
Characterize resistor using 4-wire ohms function of DMM before use.
NOTE
The temperature coefficient and temperature change of the 4
Ω
resistor when
passing current at full load must be low enough so that the change in resistance
does not cause incorrect readings. This is summarized in the following equation:
Where: VOUT is the Model 2308 output voltage
R is the characterized value of the resistor
Δ
R is the change in resistance caused by heating
V
OUT
R
R
Δ
+
(
)
-----------------------
25% of Model 2308 amps specification
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