MKS UniMag 971, Operation And Installation Manual, Page: 32 / 44

971 UniMag ™ Operation manual 29
Q: The first character is sometimes lost in the transducer digital communication reply?
A: This can be caused by too fast transducer communication reply. See RS delay command description
page 11.
Q: Is it necessary to use the ground wire between RS485 communication equipment and transducer?
A: Yes - both RS232 and RS485 communication requires a 3 wire connection between transducer and
communication equipment.
Calibration and adjustment
Q:
How often does the transducer require calibration or Zero adjustment?
A: Calibration of cold cathode sensor is normally not required. The reading in the low range can be user
calibrated by use of the VAC3 command.
Q: How long is the warm up time before obtaining reliable measurements from the transducer?
A: Reliable measurements are typically available within 5 minutes.
Q: Will the transducer retain user calibration after power is shut off?
A: Yes - all transducer parameters including calibration data are stored internally in the transducer non
volatile memory.
Service and repair
Q:
Can the sensor element be cleaned if contaminated?
A: Yes – The cold cathode internal sensor chamber can be cleaned using solvents compatible with 304
stainless steel 403 stainless steel, Ceramic (Al
2
O
3
), Viton
®
and epoxy resin.
Q:
Can the sensor element be changed if contaminated?
A: Yes - the cold cathode anode module can be changed or cleaned. Refer to Service and Repair page 31.
Q: How offend does the Cold Cathode sensor require cleaning?
A: Contaminants such as oil vapors from oil lubricated for pump will cause carbonaceous deposits which will
affect sensitivity of the gauge. The cleaning interval depends on contamination type and pressure range, but
can be down to a few hundred of hours of Cold Cathode operation time. Cold Cathode time on can be read
by using the command: @254TIM2?;FF
The anode module can be removed and mechanical polished or replaced.
Q: +24 VDC supply voltage has been connected to analog . Is the transducer damaged?
A: Likely - the analog output is not protected against applying power to the output pin.
Q: Reverse voltage has been connected to power supply input. Is the transducer damaged?
A: Not likely – the transducer power supply circuit has reverse voltage and over voltage protection however.
MKS cannot guarantee that the transducer will not be damaged.
Q: The status LED is constantly illuminating red?
A: The red status indicates a defect sensor element. Refer to Service and Repair page 31.