TB 9-6625-1188-24
IDENTIFICATION AND DESCRIPTION
1. Test Instrument Identification.
This bulletin provides instructions for the
calibration of Clip-On Dc Milliammeter, Hewlett-Packard Models 428A and 428B. The
manufacturers' manuals were used as the prime data sources in compiling these
instructions. The above equipment will be referred to as the TI (test instrument)
throughout this bulletin.
a. Model Variations. Model 428A has a current range from 3 to 1000 mA full scale,
and model 428B from 0.1 mA to 10 A full scale. Only model 428B has the +12 and -7 Vdc
power supply.
b. Time and Technique. The time required for each instrument is approximately 1
hour, using the dc and low-frequency technique.
2. Forms, Records, and Reports
a. Forms, records, and reports required for calibration personnel at all levels are
prescribed by TB 750-25.
b. Adjustments to be reported are designated (R) at the end of the sentence in which
they appear. When adjustments are in tables, the (R) follows the designated adjustment.
Report only those adjustments made and designated with (R).
3. Calibration Description. TI parameters and performance specifications which
pertain to this calibration are listed in table 1.
Table 1. Calibration Description
Test instrument parameters
Performance specifications
Power input requirements
115 or 230 V 10%, 60 Hz, 70W
Current ranges:
428A
3 to 1000 mA full scale
428B
1 mA to 10 A full scale
Accuracy
(3% FS + 0.1 mA)
EQUIPMENT REQUIREMENTS
calibration procedure. This equipment is issued with Secondary Transfer Calibration
Standards Sets AN/GSM-287 or AN/GSM-705. Alternate items may be used by the
calibrating activity when the equipment listed in table 2 is not available. The items
selected must be verified to perform satisfactorily prior to use and must bear evidence of
current calibration. The equipment must meet or exceed the minimum use specifications
standard and TI. Where the four-to-one ratio cannot be met, the four-to-one accuracy of the
equipment selected is shown in parenthesis.
