Sutron Xpert2, Operation And Maintenance Manual

Page: 278 / 336

Bringing the Benefits of Real-Time Data Collection to the World
Sutron Corporation, Tel: 703-406-2800, http://www.sutron.com
268
Operational States
The ADC has two operational states - running and stopped - which are controlled by commands
to the device.
Running
In this state, the input lines are sampled and processed. This state consumes more power than the
stopped state, so the ADC card should be left running only if necessary. The digital output line
may be pulsed using the pulse command. The ADC executes a reset sequence when it receives
the run command. When the reset is complete, a message is sent to the host.
Stopped
In this state, the device is idle. It will accept commands, and the output SwGnd will reflect the
last command that set this output to either open (1) or switched to ground (0). The input lines are
not sampled. Pulse commands will be ignored in this state.
Inputs/Outputs
Inputs
The ADC has six single ended analog inputs which may be paired to form differential inputs.
Outputs
The ADC provides:
One 12-volt output (Bat)
One switched 12-volt output (SwBat)
One output that can be switched to ground (SwGnd)
Six excitation channels (analog outputs) that can be programmed from –5V to +5V, and,
One output –Ex which is always the negative of the current excitation voltage value.
The excitation channels are shared with the input lines. Only one excitation channel can be active
at a time. The negative of this voltage provided on –Ex can be useful in balanced bridge
applications to minimize common mode voltage.
The output SwGnd provides a switched path to ground that, when closed, grounds through a 100-
Ohm resistor. The state of this output may be pulsed using the pulse command. It may be pulsed
open or closed. If the output is already in the state that the pulse command requests, nothing will
happen. The ADC device must be in the running state to pulse SwGnd.
The board must be in the running state to switch the SwBat on. This will turn off if the device
goes to the off state.
Analog Measurements
The ADC can measure voltages on its terminals and across internal sense elements. Sense
element voltages allow currents to be calculated by a host processor. The ADC can also take
paired terminal voltage and sense element voltage measurements that can be used to compute
resistance values.