Voltage, Current and 0-20Ma Current Loop Measurements
20 Channels per Module
Auxillary Alarm I/O
Programmable Measurement Types
Alarm Levels and Scaling Functions
The 911 modules provide 20 channels of voltage and current measurement at 17 bit resolution and 1uV integrity and is fitted with general purpose disconnectable screw terminals. It can be used to measure standard 4-20mA current shunts for this purpose. The number of channels committed to current measurement is determined when the unit is built. Without current shunts fitted, this module provides voltage measuremet at lower cost than the 910 with the added convenience of disconnectable terminals. External current current shunts can be used but accuracy is dependant on the integrity of connections and shunt used.
They can be programmed to integrate signals to be measured over one complete mains cycle (50 or 60Hz) allowing the 911 to reject large amounts of mains borne interference superimposed on microvolt signals. During a measurement the interface is continually monitored and should it exceed the dynamic range of the measurement made an error is reported (a higher range is selected in Autorange).
Measurements can be made continuously or under direct command from the host computer and can be returned in one of several formats most convenient for the supervisory software
The 911 module has three digital outputs and a digital input which can be used in combination to drive a local alarm indicator. Two alarm outputs can be set by any channel outside a high (first output) or low alarm limit (second output). High and low limits can be programmed for each channel together with a threshold deadband to ensure single transitions to alarm state. The digital output level is suitable to drive smalll externally powered relays using an isolated supply
The third is an isolated relay output can be used to drive an audible alarm. The alarm output can be 'Acknowledged' and cancelled by a contact closure to the digital input. te output will switch again when any new alarm or channel error condition occurs.
Note: The two alarm outputs and the acknowledge inputs are not isolated from the RS485 communications port