902B Abs Piezo
Operation manual
49
FAQ (Frequently Asked Questions
)
Applications
Q:
Can the transducer and sensor element continuously withstand vibrations from a mechanical fore-pump.
A:
Yes – the Piezo sensor element can withstand continuous vibrations.
Q:
Is the transducer compatible with fluorine gases?
A:
Yes – The Piezo sensor is compatible with any gas compatible with stainless steel 316.
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 outgassing, mainly by water vapor. The pressure can easily rise to a few torr over time.
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 Piezo sensor element is extremely robust to mechanical forces and can withstand continuously
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:
The 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 0.2 A @ 30 VDC
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 maximum length of the analog cable depends on cable quality and the electrical noise environment,
but a cable length 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.
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?
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.
Measurement, Calibration and adjustment
