Welch Allyn Inc.
Aneroid Sphygmomanometers Service Manual
Revision A
Welch Allyn Inc.
Page 25 of 40
6.2 Calibration of the Silver Ring Hand Aneroid
1. Obtain gage assembly, attach air supply with luer fitting
2. Position test dial and test pointer on gage
.
3. Apply 300 mmHg pressure. View gauge and ensure the leak is no greater
than 10 mmHg in 5 seconds.
SPAN ADJUSTMENT
From average "0" starting position, pressure gage to 320 then down to 300
mmHg. Note position and maintain pressure:
1. If span is too low - obtain tweezers or jewelers screwdriver and bend the
adjustment pin away from pinion parallel to gear sector arm. Change
pressure to 0, make sure to re-adjust the test dial so that the pointer will be
slightly left of the graduation line. Re-pressurize to 320 then to 300 to
evaluate effects of adjustment.
2. If span is too high - obtain tweezers or jewelers screwdriver and bend the
adjustment pin towards the pinion parallel to the gear sector when
pressurized at 300. Change pressure to 0, make sure to re-adjust the test dial
so that the pointer will be slightly left of the graduation line. Re-pressurize to
320 then to 300 to evaluate effects of adjustment.
3. Repeat above steps as required to obtain correct span adjustment.
LINEARITY ADJUSTMENT - (As required) If 0 and 300 position are correct, and
other points at 250, 200, 150, 100 or 60 are either too high or too low at one or
more points, then perform the following adjustments.
HIGH GAGE READINGS - (Predominantly at 250 and 200)
1. Remove test pointer and test dial. Obtain calibration tool and position over
adjusting pin down to cross shaft, (move gear sector with finger of other hand
to allow access). Rotate pin to move hook away from diaphragm approx. 15
degrees. While maintaining this position, lift tool up from cross shaft approx.
1/16 inch and bend the pin back towards the operator approx. 15 degrees.
Lift the calibration tool up to the point where the pin makes contact with the
gear sector and bend the pin up, (away from operator) approx. 30 degrees.
2. Remove tool and release gear sector. The resultant bend should result in the
gear sector starting position being a max. of 2 teeth extending beyond the top
plate when viewed from a top position and a minimum of 2 teeth within the
edge of the top plate. (This must be checked by pushing the gear sector 2
teeth from the other side of the top plate). Adjust secondary bend if gear
sector is out of these limits. Re-assemble test dial and pointer, recheck span
and adjust as necessary prior to inspection at intermediate points.
