introduction 
cyber®-tx is a microprocessor based pcb product, designed for gas sensing applications. it may be used together with a co or h2s  lectrochemical cell, a catalytic gas sensor for  flammable gases, or an  infrared sensor for co2 or hydrocarbon gases and vapours. the raw signal input from the sensor is processed digitally by the microprocessor, which also stores information such as calibration data, the range and lifetime of the sensor. the device can be configured to deliver the sensor readings as linear analogue outputs (0.4-2v or standard 4-20ma). cyber®-tx can also be interrogated digitally via rs485, with information such as alarm thresholds, fault conditions, calibration information etc being available from the microprocessor’s registries.
structure
cyber®-tx is built around a 12bit microcontroller. it provides analogue outputs and a serial output rx/tx to facilitate communication.
a number of versions of the device are available, depending on the gas sensor with which it is being used:
- catalytic sensor (single or matched pair) for combustible gases detection;
- electrochemical cell for toxic gas detection;
- infrared (ir) sensor for co2 and/or hydrocarbon detection.
various circuits are implemented in accordance with the sensor used and the application:
- the self test circuit (for the co cell);
- zero drift compensation circuit.
operation
the main board is provided with some basic information written in the microprocessor’s memory:
- lot/serial number
- calibration date
- span factor (for catalytic sensor)
- alarm thresholds
all the above are written in the registries and are available for reading using the digital output.
other output data available:
- the present measured gas concentration on demand (in ppm or %lel depending on the sensor used)
- alarm condition
- fault condition
- the age of the sensor (depending on the application)
according to the board version, through the respective protocol, all the above in formation is available for readout.
a 0.4 - 2v analogue voltage signal is also included as standard.
a standard 4 - 20ma current output is also available for remote analogue monitoring purposes, using an optional second pcb, allowing cyber®-tx to be used as a simple 4 – 20ma transmitter if required.
notes:
1. span/rank - for a catalytic gas sensor, monitoring combustible gases, the relative esponse of the target gas is used to determine the range of the device.
the readout drift in gas is memorized as the span, together with the zero value when calibrating the device.
for some electrochemical cells, a rank se-lection gives the drift in na/1ppm of co detected.
the span or rank respectively, depending on the application, is memorized in the icroprocessor’s registries.
2. lifetime - the lifetime of the electrochemical cell is usually 2-5 years, depending on the manufacturer specifications, provided the measured output does not fall bellow a certain percentage of the original output. the microprocessor’s software is provided with a
timer, counting the time elapsed from the sensor’s first calibration. a fault signal is rovided on the serial output after the programmed number of years, stating that cell should  be replaced.
3. auto-zero – the drift of the zero indication in time affects the reading of the actual gas level so it is automatically compensated.
the software implemented contains a routine which compensates for the drift in zero level.
4. self-test – for the co electrochemical cells, as defined by standards, a self test routine is included, which monitors the sensor’s electrodes for short circuit or open circuit faults. the microprocessor will indicate a short or open circuit by means of the on-board fault signal.
also, in case of electrolyte leakage in significant quantity or in case of complete drying of electrolyte, the self test will activate a fault output to warn of the imminent failure of the cell.(n.b. – the function is available on the nemoto electrochemical cells only)
5. ack/peak – an input is provided instead of alarm 2 to acknowledge the alarm signal, if requested or to provide the peak concentration level from the last acknowledgement on.
6. buzzer – an output is provided instead of alarm 1 for a buzzer if necessary.
pin desc-ription


if provided with main board only, the pin assignment is as in the upper drawing.