The Orbis Heat Detector monitors temperature by using a single thermistor which provides a voltage output proportional to the external air temperature.
Orbis heat detectors have an open-web casing which allows air to flow freely across a thermistor which measures the air temperature every 2 seconds. A microprocessor stores the temperatures and compares them with pre-set values to determine whether a fixed upper limit–the alarm level–has been reached.
In the case of rate-of-rise detectors the microprocessor uses algorithms to determine how fast the temperature is increasing. Static heat detectors respond only when a fixed temperature has been reached.
Rate-of-rise detectors also have a fixed upper limit but they also measure the rate of increase in temperature. A fire might thus be detected at an earlier stage than with a static detector so that a rate-of-rise detector is to be preferred to a static heat detector unless sharp increases of heat are part of the normal environment in the area protected by the heat detector.
Orbis detectors have drift compensation to compensate for changes caused by the environment. The most usual change is contamination.
If the detector is dirty to the point where it can no longer compensate, its LED will flash yellow while it is in StartUp.
When Orbis detectors are powered up they automatically enter a phase known as StartUp and in which they stay for 4 minutes. After this they revert to normal operation. If the detector is reset, ie, if power is disconnected for one second or longer, the detector will always enter StartUp for the first four minutes after power has been restored. The detector LED flashes red once a second to indicate that it is in StartUp.
What StartUp indicates:
StartUp is used to check that the positive and negative cables are connected in the correct polarity and that power has been applied to the detector. If this is the case, the LED will flash red once a second.
StartUp will not check whether the IN+ and OUT+ connections have been transposed. This is not a problem if standard bases are used as the detector will operate normally.
If, however, diode bases are used and a detector is removed from a base with transposed positive connections none of the detectors beyond this point will operate.
Orbis detectors incorporate a test facility known as FasTest®, a facility which is automatically available during StartUp and which modifies algorithms so that testing is possible within 4 seconds.
The environmental performance is similar to that of the Orbis optical smoke detector but it should be noted that heat detectors are designed to work at particular ambient temperatures.