Specifications

MODEL 370 REV: D Page 13 of 26
interface buffers provide I/W communications through the IEEE 488 interface.
Switch SW1 at the rear panel determines the IEEE bus address for the instrument.
Binary coding is read during power on initialization.
4.1.3 Software
At power on, a start up routine initialixes the system and displays the power on
message.
The displayed readings are calculated from:
A/D data (binary) * 2 * V
ref
* Calibration * A/unit
Linear = —————————————————————
32678 * Gain V/A
Logarithmic readings are calculated using Log
10
Software. All data values are
calculated using floating point routines.
4.1.4 Power Supply Circuitry
The standard IEC line connector P10, fuse F1 and line voltage selector switch SW2
provide AC voltage to power transformer T1. Isolated low voltage AC from the
transformer is rectified, filtered, and regulated to 5VDC by diodes CR5, CR6,
Capacitor C7, and U5. U19, a power supply inverter, provides -5V for the analog
circuitry.
5.0 USER ADJUSTMENT, PERFORMANCE VERIFICATION, AND
CALIBRATION INFORMATION
Sections 5.1 and 5.2 describe adjustments and measurements to verify the
performance of the Model 37. Section 5.3 describes the calibration data format in
the EPROM
5.1 LCD Viewing Angle
The viewing angle of the LCD display may be adjusted by turning the
potentiometer on the rear of the instrument. Adjust the potentiometer for best
contrast and viewing angle.
5.2 Performance Verification
The accuracy of the Model 370 may be verified using a precision current source
such as a Keithley Model 220 or equivalent. The Model 370 will change range as
the signal causes the display to increase beyond 24000 counts. Verify accuracy by
comparison of indicated currents to the accuracy table in the specifications section.
5.3 Calibration Data Format
Calibration information is stored in the 32K x 8 EPROM starting at hex memory
address 6000 in standard Intel hex format. The format of the calibration EPROM is
as follows:
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