Fluke 45 user manual Response Times

45

Users Manual

CIRCUIT	LOAD
					45 DUAL DISPLAY MULTIMETER
	V		10A
	600V CAT I	!									CAL
	1000V CAT I
											ENABLE
	COM		100
			mA
		FUSE F1	V	A					REL	dB	2ND
		500 mA
		F 250V							REF#	REF	LOCAL
	FUSED		V	A	FREQ	AUTO
									HOLD	MN MX	RATE
						COMP	HI	LO	THRESH	ADDR	BAUD
									POWER
									2ND
		V			A
											aam17f.eps

Figure 4-2 DC Voltage and DC Current Measurement on Input Signal

The lead from the internal measuring circuitry of the meter to the COM binding post (on the front panel) is the same for both voltage and current measurements. The resistance of this lead is approximately .003 Ω . If current is being measured, therefore, a voltage drop will occur in the resistance that is common to both circuits. This internal resistance, when added to the external resistance of the lead from the COM input terminal will affect the accuracy of the voltage reading. For instance, if the external lead resistance is .007 Ω , the "total" common resistance is .010 Ω . If there is 1 A of current, the voltage reading would be affected by

(1 A x.01 Ω ) = .01 V or 10 m V.

Depending on the circumstances, this may be significant.

If you want to measure dc voltage on an input signal in the primary display and dc current in the secondary display, proceed as follows:

1.Turn the meter on.

2.Press Yto select the dc voltage function for the primary display.

3.Press S, then press Cto select the dc current function for the secondary display.

4.Connect the leads to the test circuit as shown in Figure 4-2 and read the measurements on the displays. Although current will be displayed as negative, it is in fact positive when interpreted according current flow convention.

Response Times

Response time is the time between a change in an input and when that change is displayed. The meter’s response time depends on many factors: the measurement function selected, number of measurements being made (single measurement when only the primary display is used, or two measurements when both the primary and secondary display are used), the input

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