MKS UniMag 971, Operation And Installation Manual, Page: 10 / 44

971 UniMag ™ Operation manual 7
The 971 is available with different input/output connectors. Use a cable with strain relief to ensure proper
electrical connection and to reduce stress on the connectors.
 Ensure a low impedance electrical connection between the 971 transducer body and the
grounded vacuum system to shield the sensor from external electromagnetic sources.
Ensure that the analog output is connected to a floating input.
To comply with EN61326-1 immunity requirements, use a braided shielded cable. Connect the braid to the
metal hoods at both ends of the cable with the end for power supply connected to earth ground.
The power supply input is 9 to 30 VDC. The power supply input is protected by an internal thermal fuse. The
fuse is self recoverable; do not replace it. Damage may occur to the circuitry if excessive voltage is applied,
polarity reversed or if a wrong connection is made.
If using the analog voltage output, connect the positive analog out and negative analog out pins to a
differential input voltmeter or an analog-to-digital (A/D) converter.
Do not connect the negative side of the
analog output to the negative side of the power supply input or to any other ground. Doing so will cause half
of the power current to flow through this wire. Measurement errors in the output voltage may be seen due to
the voltage drop from this current. The longer the cable, the worse the error will be. Do not connect the set
point relay terminals to the analog output.
Correct connection of analog output to floating input
Incorrect connection of analog output to none floating input
High Voltage Control
The 971UniMag must be controlled externally to ensure that the high voltage is not enabled at pressures
higher than 5×10
-3
Torr. The protect setpoint feature prevents continuously operation at high pressures,
however it should not be used as control function for the high voltage.
Refer to page 8 and 15 for control options.
Continuously operation over 5×10
-3
Torr and fast pressure spikes with the high voltage enabled
can damage the cold cathode sensor element or cause shift in calibration.