Maintenance
operations
Analogue
calibration
The ADC & DAC Test option inside TRY1401 is provided to
calibrate the ADC inputs. This involves opening the
Power1401-3, since the ADC trimming controls are manually-
adjusted potentiometers (see page 36 on taking the lid off.)
Before we ship your unit, we run this program and set the
waveform system to an accuracy of approximately 0·5 mV, or
three least significant bits (LSBs). On the
5 V range, one
sixteen-bit LSB corresponds to only 150
V, which is of the
same magnitude as the drift caused by the normal ageing of
components. Therefore, if accurate voltage measurement is
important to you, we suggest that you calibrate your Power1401
against a known standard as part of your experimental
protocols, and check the absolute accuracy once every six
months. We find that most units drift by substantially less than
thirty-two LSBs (0·05%) over this period.
To make use of this program you will need a fine trimming tool
or a 1·4 mm flat-bladed jeweller’s screwdriver, a few BNC-to-
BNC cables and a BNC tee-junction, and an accurate digital
voltmeter (DVM) with a resolution of 10
V on the ±5 V range.
It is most important that you allow the Power1401 to warm up,
with power on for at least thirty minutes before you start the
calibration, to allow the system to reach thermal equilibrium.
Equipment needed
Alternatively, you may choose to return your Power1401 to
CED for calibration. See page 46 for advice on sending it back.
To run TRY1401, select
Running TRY1401
Start, All Programs, 1401 support, TRY1401
ADC & DAC Test
is an option inside
Tests
. The screen
instructions detail the equipment required and the actions taken
at each step. The procedure involves calibrating the DACs
against the DVM, then calibrating the ADC against DAC0.
When working inside the Power1401 take precautions against
static electricity. The case is connected to mains earth via the
power cable; earth yourself to the case, preferably via a wrist
strap.
Electrostatic
precautions
42
Summary of Contents for Power1401-3
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