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BT57i ORP sensor User’s Guide
Short description
The ORP sensor BT57i measures the ability of a solution to act as an oxidizing or
reducing agent. ORP stands for oxidation-‐reduction potential also known as Redox
Potential.
The ORP sensor consists of an ORP electrode and an amplifier. The ORP electrode
has two components: a
measuring
half cell comprised of platinum metal immersed
in the test solution in which the redox reaction is taking place, and a
reference
half
cell (sealed gel-‐filled Ag/AgCl) surround by salt solution. The measuring platinum
electrode serves as an electron donor or electron acceptor depending upon the test
solution and the reference electrode is used to supply a constant stable output for
comparison. The ORP electrode measures the redox potential – difference in the
voltage generated by the platinum measuring electrode and the voltage produced by
the reference electrode -‐ in the range of -‐450 to +1100 mV. Readings toward the
positive region of this range indicate a strong oxidizing agent, while readings toward
the negative region indicate a strong reducing agent.
The ORP electrode has been built into a long plastic tube with an opening at the
bottom side and is supplied with a storage bottle containing a protective solution.
When the ORP electrode is not being used, it must be kept in the storage bottle.
During measurements the electrode must be dipped in the solution for roughly 1 cm.
The electrode is connected to the amplifier by means of a coax cable and a BNC
connector.
The CMA ORP sensor can be directly connected to the analog BT inputs of the CMA
interfaces. The sensor cable BT -‐ IEEE1394 needed to connect the sensor to an
interface is not supplied with the sensor and has to be purchased separately (CMA
Article BTsc_1).
Sensor recognition
The ORP sensor has a memory chip (EEPROM) with information about the sensor: its
name, measured quantity, unit and calibration. Through a simple protocol this
information is read by the CMA interfaces and the sensor is automatically recognized
when it is connected to these interfaces.
If your ORP sensor is not automatically detected by an interface you have to
manually set up your sensor by selecting it from the Coach Sensor Library.
Calibration
The CMA ORP Sensor BT57i is supplied calibrated. The output of the sensor is linear
with respect to the redox potential. The supplied calibration function is:
V(mV) = 464.84 * V
out
(V) – 557.08
