RBMS Plus Installation and Opera
RBMS Plus Installation and Operation Manual
Alpha Technologies Ltd. | www.alpha.ca
PAGE 8
0370260-J0 Rev B
2.
2.1.
Battery Sensor Description
Sensor modules are small, inexpensive units designed to mount in close mechanical, electrical and thermal proximity to
the monitored jar’s terminal posts. The sensor takes a very small amount of “idling” power from the monitored jar
(typically less than 10 mA). Internally, a programmable microcontroller chip provides an optically isolated
communications interface for the site control unit. Sensors are connected to the RBMS Plus using a CAT5 cable daisy
chain.
The sensor continuously monitors the voltage and temperature of the jar. At user-defined intervals, the microcontroller
generates a digitally synthesized AC test signal of approximately 0.5 to 6.0 amps (depending on sensor type) which
drives the jar’s terminals for testing purposes. This test current causes a small AC voltage, proportional to jar
impedance, to be superimposed on the jar’s DC terminal voltage. This AC voltage is separated from the DC terminal
voltage and amplified inside the sensor module. It is then fed to an analog-to-digital converter inside the
microcontroller chip. The microcontroller digitally samples the AC waveform and performs a DSP (digital signal
processing) algorithm that filters out noise and measures the amplitude of the AC signal. These measurements and
subsequent calculations determine the jar’s internal AC impedance, which is the basis for admittance measurements.
Mechanically, the sensor consists of two wires with terminal lugs that connect to the jar’s positive and negative
terminal posts, and an electronics assembly that contains the test signal generation and measurement circuitry.
The two wire sensors have the advantage of working with a wide variety of jar mechanical configurations. Each sensor
is shipped with a 1’ CAT5 cable to connect the sensor to the daisy chain. This cable is the proper length for most
applications. Longer cables are available from PBT.
2.1.1.
“Low Voltage” Sensors
The RBMS Plus system is used in environments where string voltages are 59 Vdc and lower. Low voltage sensors are
appropriate to be used in these low voltage strings.
CAUTION: Installing low voltage sensors on a high voltage string will damage the sensors and may present a shock
hazard.
Sensors will be auto-discovered by the controller. These low voltage sensors have the advantage that their position in
the string is automatically discovered. This means the sensors can be connected in any order and the controller will
automatically discover which cell or jar the sensor was installed upon.
Each sensor has a bi-color red/green LED that indicates the operational state of the sensor and its communications
status with the RBMS Plus. Each sensor is also is internally fused so that improper connection to the jar will not damage
the jar, the jar cabling or the sensor. The sensors are fully optically isolated from the RBMS Plus.
2.1.2.
Sensor Selector Guide
The standard RBMS Plus system 0370260-002, ships with power cable, CAT5 cable and 4 battery sensors. When two
battery strings are required to be monitored then order 0370260-003.
