TB 9-6625-1185-24
IDENTIFICATION AND DESCRIPTION
1. Test Instrument Identification.
This bulletin provides instructions for the
calibration of Megohmmeter, Freed Transformer, Models 1620, 1620B, and 1620D. The
manufacturers' manuals were used as the prime data source in compiling these
instructions. The equipment being calibrated will be referred to as the TI (test instrument)
throughout this bulletin.
a. Model Variations. Variations among models are noted in tables and text.
b. Time and Technique. The time required for this calibration is approximately 2
hours, 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
Dc voltage
Model 1620
Range: 50 to 1000 V dc
Accuracy: 2% FS
Model 1620B
Range: 250 to 2500 V dc
Accuracy: 2% FS
Model 1620D
Range: 5 to 1000 V dc
Accuracy: 2% FS
Model 16201
Range: 0.1 to 4,000,000 megohms
Accuracy: 5%
Model 1620B1
Range: 1 to 2,000,000 megohms
Accuracy: 5%
Model 1620D1 2
Range: 0.01 to 40,000,000 megohms
Accuracy: 5%
Not calibrated above 10,000 megohms.
1
Not calibrated below 0.1 megohms.
2
EQUIPMENT REQUIREMENTS
calibration procedure. This equipment is issued with Secondary Transfer Calibration
