ennoLogic eM870M Insulation Multimeter
Function Descriptions
22
3.2.4 Frequency & Duty Cycle of Digital Signals and Temperature Measurements
To measure the frequency or duty cycle of a digital signal, set up the meter as shown in Figure 3-4. Please note that the peak to
peak voltage of the digital signal must be between 2.5V and 5V, its frequency in the range of 5Hz ~ 2MHz, and its duty cycle
between 5% and 95%. Duty cycle refers to (pulse width of high cycle / total period of rectangular waveform signal) x 100%.
The same rotary switch position and connection terminals are used to measure temperatures with the enclosed thermocouple
probe.
1.
Turn on the power switch and set the rotary switch to position .
2.
When performing frequency and duty cycle measurements of digital signals, insert the test leads into the
V
Ω
Hz
and
COM
terminals respectively. When performing temperature measurements, connect the positive/red plug of the thermocouple to
the
V
terminal and the negative/black plug to the
COM
terminal.
3.
Press the
Hz/Duty
key to select frequency (Hz) or duty cycle ( ) measurement mode.
4.
For frequency and duty cycle measurements: connect the test leads/probes to the circuit being measured. Read the
displayed value. If the frequency of the measured signal is lower or higher than the meter’s measurement range, the display
will show zero. If the amplitude of the signal is too low or the low level is larger than 1 Volt, the display will also show
zero. Note that the meter will always auto range for frequency and duty cycle measurements. Pressing the
RANGE
key has
no effect.
5.
For temperature measurements: press the
SELECT
key to select temperature measurement mode. If the meter’s input
V
and
COM
terminals are not connected to a thermocouple, the ‘OPEn’ symbol will be displayed. Connect the positive/red
plug of the thermocouple to the
V
terminal and the negative/black plug to the
COM
terminal, and read the displayed
temperature value. Press the
RANGE
key to select Celsius or Fahrenheit. If the measured temperature is higher than the
meter’s measurement range, it will display the internal temperature of the instrument and the ‘OL’ symbol.
Hz
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