Chapter 4
Theory of Operation
4-2
www.natinst.com
The major components of the SCXI-1112 modules are as follows:
•
Rear signal connector
•
SCXIbus connector
•
SCXIbus interface
•
Digital control circuitry
•
Analog circuitry
The SCXI-1112 modules consist of eight multiplexed input channels, each
with a fixed gain of 100. Each input channel has its own lowpass filter. The
SCXI-1112 modules also have a digital section for automatic control of
channel scanning, temperature sensor selection, and calibration.
Rear Signal Connector, SCXIbus Connector, and SCXIbus Interface
The SCXIbus controls the SCXI-1112 module. The SCXIbus interface
connects the rear signal connector to the SCXIbus, allowing a DAQ device
to control the SCXI-1112 module and the rest of the chassis.
Digital Control Circuitry
The digital control circuitry consists of the Address Handler and the
following registers: Module ID, Configuration, EEPROM, and Channel.
The Address Handler controls which register is being addressed. The
Module ID Register contains a code unique to the SCXI-1112 module. The
Module ID is 33 decimal.
The Configuration Register configures the SCXI-1112 modules for the
desired scanning mode and connection to the rear signal connector. The
EEPROM Register is the address for interfacing with the module
EEPROM, which contains calibration information. The Channel Register
selects a channel for a single measurement or a start channel for a scan.
Refer to
in Chapter 1,
learn about options for programming the control circuitry.
Analog Circuitry
The analog circuitry per channel consists of a lowpass filter and an
amplifier with a fixed gain of 100. The CJSENSOR channel also has a
buffered lowpass filter but has no amplifier. The channels and CJSENSOR
are multiplexed to a single output buffer.
