LESSON 4
NULL DETECTOR 845R
TASK
Describe and identify theory, terminology, operation, and troubleshoot Null
Detector 845AR.
CONDITIONS
Given information and illustrations about theory, terminology, operation,
and troubleshooting of Null Detector 845AR.
STANDARDS
Demonstrate competency of the task skills and knowledge by correctly
responding to 80 percent of the multiple-choice test covering Null Detector
845AR.
REFERENCES
Technical Manual for Fluke Model 845AR Null Detector
Learning Event 1:
DESCRIBE THE 845AR NULL DETECTOR
1.
The Fluke Model 845AR High Impedance Voltmeter-Null Detector allows
measurement of dc voltages from 1 microvolt to 1000 volts dc in 19 ranges.
When used as a null detector on the 100-millivolt range and below, the input
impedance is an excellent 10 megohms. A linear recorder output allows the
instrument to be used for production testing, and also a dc amplifier with a
maximum gain of 120 db.
2.
The instrument may be wired to operate from a line power source of 115
volts ac or 230 volts ac, as desired.
The instrument is designed to be
mounted directly in a standard ETA 19-inch relay rack. Resilient feet are
also provided for bench top use.
3.
Electrical specifications.
a. Input voltage range. 1 microvolt to 1000 volts dc end scale in 19
ranges, using X1 and X3 progression.
b. Input resistance. 100 megohms on 300 millivolt range and above; 10
megohms on 100-millivolt range and below.
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