Objective - University of Wisconsin–Madison



Objective

This lab is meant to be an instructional manual on how build a device to test gauges. The device can be constructed using parts commonly found in hospitals.

Equipment

1. Blood pressure cuff

2. T-valve

3. Precise Gauge

4. Test Gauge

5. proper tubing

Procedure

1 collect the parts listed in the Equipment section. They may look different than the ones pictured below.

(insert pics that are spliced together)

2 Connect the cuff to the T-valve

3 Connect the accurate gauge to any of the two remaining open connections.

4. Connect the gauge under test to the last open connection on the T-valve.

5. Wrap the cuff around something solid. This will allow us to produce pressure in the cuff. In our example, a roll of paper was used. As the cuff is pressurized, it will squeeze down on the item inside the cuff and will provide the pressure measurements needed to test the gauges.

6. Squeeze the bulb attached to the cuff. You should notice the pressure readings on both gauges going up. If you don’t notice any changes check the connection to make sure they are secure and not letting air out.

7. Pressurize the test gauge to 200 mm Hg. Note the actual pressure on the accurate gauge. The pressure should be the same. If not, note any differences of the gauge under test reading and the accurate gauge reading.

8. Slowly release the pressure using the knob located on the bulb. You should notice the needle of both the gauges going down at the same rate. Stop the release of pressure at increments of 20 mm Hg. Note the difference in pressures at these points. An acceptable value of deviation is 3 mm Hg. If it is off my more than 3 mm Hg, manual corrections may have to be made.

9. repeat step 8.

(some pictures might fit here)

10. Pressurize up to 200 mm Hg on the accurate gauge. Release pressure to 120 mm Hg noting the difference between the readings every 20 mm hg. Re-pressurize to 200 mm Hg and repeat step 8. This is jus a precaution to make sure the inner workings of the gauge stay consistent.

11. If the deviation varies at different pressures, note what the gauge under test reads at the correct pressure measured by the accurate gauge.

Manual Corrections

Disclaimer:

There are many different kinds of pressure gauges. This guide to fix the deviation of a gauge is in no way guarantied to work for each of them. IF the gauge you have looks like the one pictured, chances are that the following procedure will work to fix the deviation, if that deviation is constant through the entire range of pressures tested in the steps above.

1. Slightly loosen the washer right below the gauge display. An adjustable-end-wrench (also known as a monkey wrench) will do the trick.

2. You can use your fingers or the wrench to twist the neck of the gauge. The “neck” in this procedure, is used to describe the part of the gauge that is typically covered by the tube connected to the cuff.

3. A very slight turn should do the trick.

4. test and repeat till desired result is obtained

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