DATUM ELECTRONICS
M425 TORQUE TRANSDUCER HANDBOOK
19
DIAGNOSTICS
GUIDE TO STATUS CODES
SIGNAL NOISE
The M425 Transducer is designed to be a sensitive device
and will show any variation in torque applied. The noise level
on the data from your Transducer should be very low but
will vary with sampling rates and averaging. The faster the
Transducer reads the torque data the more signal noise you
will see. (See table 3 on page 13). This table assumes that
no averaging has been applied in the instrument or software
interface. From the table you will see that at 4 samples per
second the noise levels are very low at less than 1 part in
120,000 and at 4000 samples per second they are below 1
part in 10,000.
To differentiate between signal noise and mechanical input
it is worth plotting the output data. At times the minor
fluctuations in torque will show valuable diagnostics data and
element of torsional vibration.
If you conclude that the noise is a true mechanical reading
but you require a steady display, either increase the damping
level of the display software or decrease the sampling rate.
Although designed to reject electrical noise, and designed/
tested to EMC Standards, the Transducer may be affected
by large varying electrical fields. Review all local switching,
generating or drive machinery.
If unsure of the status of the data we may be able to assist if
you send a log file and a brief description of any effects you
are seeing to:
INCORRECT TORQUE
Check the scaling of the output device.
If using the user software on a PC look at the torque
calibration tab.
The certificate issued with the transducer will have a value for
its output signal in mV/V at a given torque.The software set
up should match this (i.e. 1.756mV/V = 250Nm)
If using the Universal Interface use the GU interface
connected via the Ethernet port and check the same tab.
Check the torque reading with no torque applied. If the
Transducer output is showing a torque reading at zero this
will be added to all readings. The torque calibration tab of
the software has an option to zero the torque reading. The
Universal Interface also has a torque zero button. Pressing
and holding this for 10 seconds will take the current torque
reading as zero.
When checking or setting the zero check to see if any torque
is locked into the transducer by the machine or rig on which
it is used. It is ideal to check the zero with the transducer
disconnected from the rig.
NO DATA
If you have no data being transmitted from the Transducer
check the LED on top of the Transducer at the opposite end
to the cable exit. This LED should be green and on. If the
LED is not on check all connections and the supply to the
Transducer.
If this LED is on and you have no data check the output:
(1)
Universal Interface
- this will show a STATUS on line 4 of
the display.
(2)
(No Serial Data out from the Universal Interface to your
device)
- if the display on the Universal Interface is reading
and showing changing torque and speed values as you
apply loads to the Transducer, check the Interface to
your system.
2A Baud Rate
- the baud rate requested for output can
be seen and changed using the software provided.
2B Signal Reversal
- some communications over RS485
are described differently and may be reversed.
(3)
Bad Data
- if you are seeing data from either the
Transducer or the Interface that appears invalid, check the
connections to your system and the baud rate. The data
when streaming in Mode 1 should appear on a simple
terminal programme.
ZERO OFFSET
The factory zero of the M425 Transducer will be declared
on the calibration sheet. If the reading you have at zero
differs from this value, look at the raw signal value from the
Transducer (either using the user interface software or the
detail command). Small offsets can be removed using the
zero command on the software interface or the zero button on
the Universal Interface. If the offsets continue to appear refer
back to the original offset value on your certificate to check
that you are not applying an ongoing series of small offsets.
If the offset is large (greater than 0.2mV/V) it is likely that
the Transducer has been subjected to a significant torque
overload and has a permanent offset. If this is the case and
repeated overloads are applied, the Transducer will become
inaccurate and may ultimately mechanically fail. You should
review your application and consider a higher rating of
Transducer.
If the keyways of the Transducer are visually out of line this
is a very good indicator that the Transducer has suffered a
significant and damaging overload.
