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6.4.3 Temperature Probe
An air-temperature probe is provided in the SF-1020i flowbench for Intake Air Temperature. It is in the
chamber under the test orifice baseplate. No maintenance is necessary for the probe; replace only if
defective.
Verify the probe by reading r
egister
40012 Temperature1
. If the flowbench has been OFF for several
hours, the reading should be at room temperature.
6.4.4 Orifice Stepper Motor Assembly
To access the range orifice stepper motor
assembly, remove the test orifice baseplate. The
only maintenance necessary is cleaning the area
around it.
The range orifice assembly is a sliding plate with
a variable, diamond shaped, sharp edge orifice
and a stepper motor, a threaded rod with the
plates attached, and two limit switches. The PLC
is programmed with a position for each range.
When a range is selected on the PLC, the motor
will drive the plates until the reading matches the
programmed value for that range.
The two limit switches signify the end stops for the orifice plates. If the orifice assembly reaches the
extreme end of its travel in either direction, it contacts a limit switch that removes power to the motor to
stop it from binding and overheating.
Another possibility is that the limit switches are out of alignment. As the range orifice approaches range 1 or
range 10, the limit switch could activate too soon. This would only cause a range error when approaching
range 1 or range 10. If this is the case, it is acceptable to adjust the limit switch to allow the orifice
assembly to “find” its range 1 or range 10.
Figure 6.8: Range Orifice Stepper Motor Assembly
6.0 Maintenance
