pg. 49
FAQ (Frequently Asked Questions
)
Applications
Q:
Can the transducer and sensor element continuously withstand vibrations from a mechanical fore-pump.
A:
Yes – the MEMS MicroPirani sensor element can withstand continuous vibrations.
Q:
Is the transducer compatible with fluorine gases?
A:
No – the 910 is not intended for use in aggressive environments like semiconductor etch applications.
Q:
When the transducer is pumped down and isolated by closing a valve the pressure is raising. Is the
transducer leaking?
A:
Not likely - when a confined space is evacuated and the pumping is stopped the pressure will rise
because of out gassing, mainly by water vapor. The pressure can easily rise to a few Torr over time.
Q:
When the transducer is leak checked on a helium leak detector. leak reading is building up slowly after
approximately 30 seconds. Is the transducer leaking?
A:
No - the internal sealing of the 910 transducer uses elastomer viton sealing and consequently helium
molecules can permeate e through the viton material and cause slow increase of helium leak readout. If a
leaking transducer is tested directly on a helium leak detector the leak is almost instant displayed.
Q:
Can the transducer be mounted in any orientation?
A:
Yes - the transducer can be mounted in any orientation without compromise of performance or calibration.
However it is recommended not to mount the transducer with the flange port facing upwards to avoid
contamination like particulates or liquids from entering the device.
Q:
Can the transducer withstand instant ventilation?
A:
Yes - the MicroPirani and Piezo sensor elements are extremely robust to mechanical forces and can
withstand continuous pressure cycles and instant air ventilation.
Q:
Can I connect a valve to be controlled by the transducer relay contact?
A:
Driving inductive loads such as valves requires special precautions. Refer to detailed description page 12.
Q:
How many pressure cycles can the transducer withstand?
A:
Both the MicroPirani and Piezo sensor element is very robust to pressure changes and there are no limits
on the number of pressure cycles. The setpoint relay contact endurance is minimum 2,000,000 cycles at
30VDC/0.2A load.
Analog output
Q:
What is the update rate of the analog output?
A:
16 times per second.
Q:
What is the maximum length of analog output cable?
A:
The length of analog cable depends on cable quality and electrical noise environment. Cable lengths up
to 100 m do not normally require any special precautions other than the cable must be screened.
Q:
The digital reading is correct but the analog output reading has some deviation from actual pressure?
A:
Check that the analog out is connected to a floating input and not an input that is connected to ground. If
connected analog out return is connected to ground, the supply current will flow in the signal line and cause
voltage drop and ground looping.
Q
:
Can I get an analog output for the Piezo signal?
A:
Yes – the analog output can be configured to any of the sensor signals. Refer to analog output set up.
Dual analog output is a hardware option. Refer to part numbers page 3.
Digital output
Q:
How fast can I request pressure measurements via the digital interface?
A:
10 times per second is the fastest recommended pressure request frequency.
Q:
How long is the waiting time from turning power on to valid measuring values?
A:
The power on sequence is approximately 2 seconds. The LED is illuminating red during power up
sequence and the digital interface will not reply to commands.
Q:
The first character is sometimes lost in the transducer digital communication reply?
