Keithley 2280 Series Reference Manual

Series 2280 Precision DC Power Supply Reference Manual Section 4: Measurement optimization
077085503 / March 2019 4-5
Autozero measurements
To ensure the reading accuracy, the instrument must measure internal references corresponding to
the zero low and gain high references. The time interval between reference updates is determined by
the integration aperture that is used for each user and internal reference analog-to-digital converter
(ADC) measurement.
By default, the instrument automatically checks the references for each triggered reading. This can
result in a longer expected time interval. This additional time can cause problems in the test
sequences in which measurement timing is critical. To eliminate the extra time, the automatic internal
reference ADC measurements can be disabled, allowing the instrument to measure only the user
portion of the reading.
When automatic reference measurements are disabled, the instrument speed per reading increases.
However, the instrument may gradually drift out of specification.
Measurement function
With autozero enabled, the
number of customer and
internal reference ADC
measurements per reading
With autozero disabled,
the number of customer
and internal reference
ADC measurements per
reading
Concurrent (V + I)
5
2
Current (I)
4
1
Voltage (V)
3
1
For example, when autozero is enabled, making 100 readings in the concurrent function with 1 NPLC
takes a total measurement time is (50 Hz power line frequency):
Total time = 5 * reading number * NPLC * (1/50) = 5 * 100 *1 * (1/50) = 10 s
When autozero is disabled, making 100 readings in concurrent function with 1 NPLC takes a total
measurement time is (50 Hz power line frequency):
Total time = 2 * reading number * NPLC * (1/50) = 2 * 100 * 1 * (1/50) = 4 s
Setting autozero
You can enable or disable automatic referencing. The reference setting is stored with the measure
function.
To set autozero using the front panel:
1. Press the MENU key.
2. Under Measure, select Settings.
3. Next to Auto Zero, select On or Off.
4. Select HOME to return to the operating display.

Keithley 2280 Series Specifications

General

Brand	Keithley
Model	2280 Series
Category	Power Supply
Language	English