Powerware Horsepower Computer System ST-2400S - Manual (Page 13)

positive and negative torque to the unit) and verify that the torque reading returns
closely to the same value. A failure here indicates a likely problem with the
dynamometer. Have the dynamometer checked by your dealer or dyno service
person.
1.3 Make sure that the load has been completely removed from the load cell.
Disconnect the load cell from the torque arm of the dynamometer by removing
the coupling fastener. If this does not correct the excessive zero offset a likely
defective or damaged load cell is indicated. You should have the load cell
checked by your dealer or dyno service person.
1.4 Make sure that the shunt resistor switch is set to the OFF position.
2. TORQUE SPAN CALIBRATION cannot proceed. This problem occurs when the
torque reading is not sufficiently close to that expected from the CALIBRATION
TORQUE value. Check the following:
2.1 Check to be sure that the CALIBRATION TORQUE is the value expected by the
2400S horsepower computer. The expected calibration torque value is normally
programmed into the 2400S by your dealer to match the calibration value and method
you will be using to check and adjust the calibration of your unit. You can check this
by setting the calibration mode switch back to the OFF position while leaving the
CALIBRATION TORQUE applied to the unit. The TORQUE display will now read
the (approximate) torque you have applied. If this value is within about +/- 10% of
the CALIBRATION TORQUE that you have applied, then it is likely that the value
expected by the 2400S for the CALIBRATION TORQUE is different than the value
you are using. Check with your dealer or dyno service person to determine the
calibration torque you should be using or use the 2400S calibration setup software to
re-program the 2400S to expect the calibration torque you are currently using.
2.2 If the TORQUE display does not read (within +/- abut 10%) the torque that you
have applied a possible defective or damaged load cell is indicated and may need to
be repaired or replaced. Have your dealer or dyno service person assist you.
Torque Calibration Notes:
There are several methods which can be used to apply a calibration torque value to the
2400S horsepower computer.
1.) Dead Weight Test Fixture: This method uses a Torque Test Bar (dead weight
test fixture) and one or more calibration weights. The torque test bar is attached
to the torque arm of the dynamometer, being careful to align the position of the
mark on the torque test bar with corresponding mark on the torque arm of the
dynamometer. Then connect the test weight(s) onto the torque test bar at the
indicated position, usually the 4 foot (1.210 meter) position. The torque produced
by the torque test bar must be accurately known, the total weight of the test
weights must be accurately known, and the horizontal distance from the center
line of the dyno to the indicated position must be accurately known. If any of
these three factors is not accurate, then the resulting calibration will not be
accurate –and the result is in-accurate torque and power readings from the
13