How does IRD8800 Series Module M88300 monitor Gap?

How does M88300 module Monitor Gap?

IRD8800 Series is a Rack-Based Machinery Protection System (MPS) manufactured by IRD Mechanalysis Limited. It is API 670 Compliant and has a variety of Modules for different purposes - like Vibration Monitoring, Speed Monitoring, Temperature Monitoring and more. For Gap Monitoring - the module in IRD8800 Series is M88300.

Module M88300 for Gap Monitoring
To Monitor Gap - M88300 uses Non-Contact Eddy Current Based Sensor as Input. The Non-Contact Sensor used for this purpose typically has a Voltage sway of 16V DC across its Total measurable Linear Gap. So, for example - if the Sensor is rated for a Gap of 0-2.5 mm - then after considering a safety gap of 0.25 mm - the sensor is used to measure a gap of 0-2 mm. This makes the Sensitivity of the Sensor 16 V/2 mm or 8V/mm or 8mV/um (200 mV/mil). Similarly, if the sensor is rated for a gap of 0-5 mm - then after considering a safety gap of 0.25 mm - the sensor is used to measure a gap of 0-4 mm. This makes the Sensitivity of the Sensor 16 V/4 mm or 4V/mm or 4mV/um (100 mV/mil).

M88300 is able to provide the required power to the Non-Contact Sensor to work. The DC Output of the Sensor is then monitored by M88300. If set for a Linear Gap of 0-2 mm - then 0mm is treated as -1mm, 1mm is treated as 0mm and 2mm is treated as +1mm - thereby making the measurement as +/- 1mm. The Sensor is locked at 0mm position (which corresponds to 10 V DC) and when the Target comes close and reaches safety gap - the Module reads it as -1 mm position (which corresponds to 2 V DC) and when the Target reaches farthest away position - the Module reads it as +1 mm position (which corresponds to 18 V DC).

Notes
So, for +/- 1mm Gap Monitoring with a 8mV/um Non-Contact Sensor - if the DC Voltage is 15V - then M88300 will read it and display it as +0.62mm. If the DC Voltage is 6V - then M88300 will read it and display it as -0.50mm