How Best to Test & Calibrate a Blood Pressure Meter?

3 February 2022

A blood pressure meter is a common household item nowadays.  This is especially so when there are elderly people in the house.  

In the old day,  we used to have a mercury type of pressure meter which they called "sphygmomanometer".

Today,  most of us will use an electronic type of blood pressure meter as shown below
The good old mercury type of pressure meters are still being used by a lot of medical personnel because it is still the most reliable and accurate pressure meter around; whereas, electronic meters will often need regular calibration and routine checking.

This article will show how one can accurately check the accuracy of an electronic meter.

What's Needed?

How to Connect up?

 1.  Connect 8-mm Silicone Tube to the mercury reservoir as shown

2.  Connection the 8-mm tube to the T-Joint

Testing 

As shown in the video,   this Omron Blood Pressure BP742 meter under test has an accuracy of about +4 mm Hg or 3% of reading @ 131 mm Hg.  it is slightly off the manufacturer's limits of +- 3 mm Hg or 2% reading.  However, it has an accuracy of -1 mm Hg or -1% of reading @ 100 mm Hg which is better than the manufacturer's limits.

Diastolic &  Systolic Pressure Readings

To complete the test,  one should also place a stethoscope underneath the handcuff to listen to the heartbeats to check the accuracy of the systolic and diastolic pressure..  

During the working process,  one can hear the meter pumping up the pressure to the handcuff and the heartbeat sounds through the stethoscope as the pressure is building up.  When the pressure goes higher than a certain set of systolic pressure,   the meter will stop pumping.  This is when one could not hear any heartbeats.  Thereafter,  the meter will slowly release the pressure and the pressure readings will drop.  Note down the reading when one first hears a heartbeat. This is systolic pressure.  With further pressure drop,  note the reading when one no longer hear the heartbeat sounds. This is your diastolic pressure.  Compare this two readings with the readings recorded by the meter.  They should be within +-3%.

Calibration

Unfortunately,  there is no adjustment allowed in this Omron Blood Pressure BP742 meter as shown in the following picture.  It would appear the calibration has to be carried out by using some kind of software and this can be done only by the manufacturer as explained by the author of this article...

How Much is a Sphygmomanometer?

The market is selling a Sphygmomanometer at a price of around SGD 40/= to about SGD 300/=.