1 – 2
Getting Started
1.1
Introduction to the Instrument
The SIM928 Isolated Voltage Source is ideally suited for applications
demanding flexibility and low-noise from a programmable voltage
source.
1.1.1
Overview
The basic function of the SIM928 is to generate a user-specified volt-
age, between
−
20 V and
+
20 V, between the
+
and
−
front-panel
terminals. The architecture of the SIM928 uses an internal battery
to power the output stage. This provides an ideal voltage source,
free of power-supply ripple. Two independent batteries are used;
while one is powering the output circuitry, the second is either be-
ing recharged or held in standby. When the output battery nears
its fully-discharged state, the standby battery is seamlessly switched
into the output circuit, and the depleted battery switched to the inter-
nal charger. With this arrangement, essentially continuous isolated
bias voltage is available to the user.
Note that, although the output stage is energized by internal storage
batteries, the control circuitry is powered externally (typically, by the
SIM900 Mainframe). Absent any external power, the SIM928 will be
o
ff
.
1.1.2
Power-on State
The SIM928 stores its operation state (programmed voltage and
on
/
o
ff
configuration) in non-volatile memory.
At power-on, the
SIM928 will return to its previous configuration after a brief system
check and initialization.
The power-on system check includes a brief test of both internal bat-
teries. If either battery appears fully discharged, it will be switched
onto the internal charger circuit; if both batteries appear discharged
(as can occur after an extended storage period), the SIM928 will not be
able to turn on the output stage. In this case, you should allow about
first use after extended storage
5–6 hours of powered operation to bring the first battery up to full
charge, at which time it will switch to the
On
state and begin charging
the second battery. This period can be shortened by power-cycling
the SIM900 Mainframe, which will cause the SIM928 to re-initiate it’s
power-on checks. Note that at least 1–2 hours should be allowed to
provide a su
ffi
cient partial charge for reasonable operation.
1.2
Front-Panel Operation
The front panel of the SIM928(see Figure 1.1) provides a simple op-
erator interface.
SIM928
Isolated Voltage Source
