Fluke 45 user manual How the Meter Makes Dual Display Measurements

Applications 4

How the Meter Makes Dual Display Measurements

level, range type (autorange or manual range), the measurement rate (slow, medium, or fast), and whether measurement types are mixed or not. (Measurements are either ac-type [ac volts or amps] or dc-type [all others]).

Typical response times for a single measurement are shown in Table 4-2. For a single measurement, results are displayed as soon as the correct range is found. However, additional time needs to be allowed for the measurement to be fully settled in order for the displayed result to meet the meter’s accuracy specifications. This "settling delay" varies, depending on the differences between the primary and secondary displays.

The settling delay is longer when ac- and dc-type measurements are mixed. Examples of mixed ac and dc measurements are volts dc and amps ac, and volts ac and amps dc. Settling times are listed in Table 4-3.

How the Meter Makes Dual Display Measurements

When the meter is in the dual display mode (i.e., both the primary and secondary displays are on), the meter takes measurements and updates the displays in one of two ways: (1) it takes a single measurement and updates both displays using that measurement; or (2) it updates each display using a separate measurement.

Note

When measuring AC + DC, (or any dual display combination of AC and DC) in the fast reading rate, the Fluke 45 may show significant reading errors. This results from a lack of filtering on the DC portion of the measurement for the fast reading rate. To avoid this problem, use only the "slow" and "medium" reading rates for AC + DC or AC and DC combinations.

Updating the Primary and Secondary Displays with a Single Measurement

The meter takes a measurement and updates both displays using that measurement only when the meter is in the autorange mode, and the measurement function and range are the same for both the primary and secondary displays.

This will happen, for instance, if dB (which always causes the voltage measurement in the primary display to autorange) or HOLD (with autoranging on) is applied to a measurement function on the primary display and the same function is selected for the secondary display.

If for example, the dB value of an ac voltage measurement were shown in the primary display and the ac voltage itself were shown in the secondary display, the meter would take a single measurement and update both displays with it.

Updating the Primary and Secondary Displays with Separate Measurements

If the measurement function, range, and ranging mode in the primary display are not identical to those in the secondary display, the meter updates each display using a separate measurement.

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