Null (Relative) Operation - Keysight Technologies 34420A Service Manual

Null (Relative) Operation

When making null measurements, also called relative, each reading is the
difference between the input signal and a stored null value. You could, for
example, make a more accurate two-wire ohms measurement by shorting the test
leads and pressing
– The null value is adjustable and you can set it to any value between 0 and ±
– The null value is stored in volatile memory; the value is cleared when power
– Each function and channel has an independent null value. For voltage
– The null value is stored in the meter's Null Register. There are two ways you
– Since an independent null value is stored for each input channel, difference or
Keysight 34420A Service Guide
Null
Read ing = measurement – null value
120% of the highest range, for the present function.
has been off or after a remote interface reset.
measurements, each input channel has an independent null. Temperature
measurement null is applied to all temperature measurements (if you change
the probe type, null is still enabled and applied). The null for resistance
measurements applies to both 2-wire and 4-wire measurements.
can specify the null value. First, you can enter a specific number into the
register from the front-panel menu or from the remote interface. Any previously
stored value is replaced with the new value. If you are operating the meter from
the front panel, entering a null value also turns on the null function.
The second way to enter the null value is to let the meter store the first reading
in the register. Press the
value and enable the Null operation. After you enable null, the first reading
displayed will be zero. If you entered a number into the register, as described
in the paragraph above, the first reading does not overwrite the stored value.
ratio functions also use these null values. Additionally, when using the
difference function, an additional difference null can be applied (the difference
null is only available from the front panel).
to remove the test lead resistance.
key to make the displayed measurement the null
Null
Front-Panel Operation 2
65