Triggering, Measuring, Calibration; Power-On Test; Measuring Functions; Input Triggering - Hameg Instruments HM 8021-4 Manual De Instrucciones

[9] DC (pushbutton) (DC coupling = button
depressed)
Selection of AC or DC coupling of the signal
input A. The bandwidth for low frequencies
is as low as 10 Hz (3dB) when the input is
AC coupled. (Input C has a fixed AC
coupling).
[10] 1:20 (pushbutton)
Selection of input signal attenuation.
Pressing this button attenuates the input
signal by 26 dB before it is applied to the
input amplifier.
[11] Auto Trigger (AC) (pushbutton)
With Auto Trigger active the counter triggers
in the middle of the input signal. Auto
Trigger always uses AC-coupling. (AC =
pushbutton depressed).
[12] INPUT A (BNC connector)
Signal input with a sensitivity of 20mV up to
80 MHz and 60 mV up to 150 MHz. The
input is protected against overvoltage up to
400 V (DC+ACpeak).
Input impedance: 1MΩ II 40pF.
[13] TRIGGER LEVEL (adjusting knob)
Continuously adjustment of trigger level.
TRIGGER (LED) 3 State trigger indicator.
The LED flashes when triggering is correct.
The LED lights when the trigger level is
above the input signal level, it is not
activated when the trigger level is below
the input signal level.
[14] 8 digit display
(7 segment LEDs, 7.65mm high)
for the measuring result (8 digit max. +
exponent).
[15] Hz: (LED) Indicates the measurement of a
frequency.
Sec: (LED) Indicates the measurement of
time.
HM 8001-2:
External Gate Input (BNC connector)
Allows the measurement of the input signal,
controlled by an external source.
Subject to change without notice
Triggering,
Measuring, Calibration

Power-on test

A practical test of the correct operation of the
HM 8021-4 is run automatically at power on. As
soon as power is applied, the display shows type
and version of the actual instrument and the
GATE indicator appears, LEDs are lit and the
Eprom and all functions of the counter are tested.
The test runs for about 2 seconds. If an error is
detected it is indicated by an "I" at the leading
digit and followed by the number of the test that
failed.
I 1 microprocessor RAM error
I 2 program ROM error
I 3 counting chain error
When the tests are completed satisfactorily, the
counter sets the display to zero and selects the
default measuring function A.

Measuring functions

FA/FC: Sets the instrument to measure the
frequencyofthesignalconnectedtoinputA/
C.
TOT.: The counter will totalize events (pulses or
cycles) on input A. Measurement stops
and display freezes as soon as the input
signal is removed or DISPLAY HOLD is
depressed. Depressing RESETcluring
totalizing clearsthe display and starts a
new measurement when releasing the
button. Reset is active as long as the
switch [7] is depressed. Totalizing A
during External Gate is performed
applying a TTL signal to the Ext. Gate
input.
PA: Sets the counter to measure the period
duration of the signal connected to input A.
TI : Sets the counter to measure the average
(AVG) pulsewidth between positive slope and
the negative slope of an input signal at
input A.

Input Triggering

As the input signal can have very different
waveforms, it is necessary to shape the signals
so that the counting circuits can handle the signals.
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