Channel and system parameters are programmed by high level instructions written to the Ethernet interface or by PI580 Windows application software. Operating parameters are stored in non-volatile memory and automatically loaded when the system is powered up or reset. Data recorders may be programmed in place or configured and programmed prior to fielding.
Programmable channel parameters are input configuration, excitation, calibration modes and levels, gain, and filter frequency. Sample rates, number of pre and post-trigger samples, trigger level and delay, power mode and autostart sequence are programmed by groups of three channels in the 5871 or two eight channel groups in the 5872. Operating parameters may be read back to verify system programming and configuration.
Data recorders are ruggedized and battery powered, allowing installation near the measurement to keep input cables short preserving higher signal frequencies. Hardware is available for mounting in 19-inch frames or enclosures.
The 5871 and 5881/3 have self-contained rechargeable batteries. A line operated power supply is available for operating and charging the battery. The 5872 and 5882 require an external battery or other power source. The 5893 is a DC-UPS that provides power from the AC line and automatically switches to battery when line power is interrupted. Programmable power modes conserve battery power when setting up or waiting for a test.
Sample timing and data recording is controlled by a PCM encoded control bus that is distributed from the Control Module to each Data Recorder. The Command Module has TTL inputs for system control including Clock, Start, Trigger and Autostart. The encoding of control signals makes the system immune to noise on the control bus that could cause false triggering and loss of data. The control bus synchronizes data recorded across multiple recorders.
The 5881 and 5882 Command Modules employ Category 5 cable for recorders within 50 meters of the Command Module. The 5883 Command Module employs optic cable for distances up to 1 kM.
A portion of the data storage memory may be used for calibration data acquired before and after test data. Multipoint calibrations are recorded by specifying the calibration mode, stimulus and number of samples for each point.
Calibration modes include voltage substitution using a programmable internal reference and four shunt resistors. Additional calibration modes measure and record excitation voltage, excitation current, zero with input shorted and gage zero without excitation.
Test data recording begins with a Start control from the Command Encoder or an Ethernet instruction. Data is continuously recorded in successive memory locations at the programmed pre-trigger sample rate. The oldest data is overwritten when the number of samples taken exceeds the total for the record.
When Trigger is received from the Command Module or internal discriminator the data recorder acquires the programmed number of post-trigger samples at the post-trigger sample rates. When all post-trigger samples are recorded, recording stops, memory is write protected and the recorder is reset for the next record. Data memory is backed-up for 40 hours by an independent power source.
The Autostart facility provides a means to automatically initiate recording of calibration and test data using a single TTL input to the Command Module. It runs a preprogrammed file that can contain up to 64 instructions. For example, it can load operating parameters, autobalance channels, select and record pre and post test calibration data, select operating power, clear write protect and start the system for test data acquisition. After data is recorded, it can power down the recorder to await debriefing.
Program instructions transfer data from channel memories to computer storage media. Data transfer rate is 450K bytes per second for a single recorder and multiple recorders are interlaced for faster debriefing. Debriefing is non-destructive. Data is not erased from the channel memory until it is overwritten with new data.
An Ethernet instruction retrieves data that provides elapsed start to trigger time. By synchronizing the start time for all recorders, data may be time correlated for recorders that triggered at different times and to other test events and data.