EBME Forums Forums Maintenance Technical Assistance PATIENT WEIGHING SCALE CALIBRATION

I was just wondering how to calibrate electronic weighing scales ( seca and the like) in a hospital environment. We have 200 electroni weighing scales in our hospital which are mostly from Seca. We can not carry 10kgs - 150kgs of weights around the hospital to calibrate and / or measure accuracy and precision of these scales. OOPs..... it would be tedious. Is there any strain gauge dummy kind of measurement that we could simulate and measure the actual weight against the displayed value in all these electronic weighing scales? I know Wellch Allyn temperature monitors have 3 different temperature probes and / or calibrators to measure, calibarate and validate at 3 different temperatures. Similar to this do we have dummy load for electronic patient weighing scales.

Electronic balances in the laboratory are easier to calibrate as weights are smaller between 1gm -5000gms but not for patient weighing scales.

Sen

Hi Senthil,

Sometime back Seca had given me a calibration procedure for the scales.

I have lost it.
We no longer are the agency

Probably you can ask Seca

Hi Sen,

In our department we have good quality weighing scales kept in calibration. We take these scales out with us and use them next to the ones we want to check, to compare readings. If any are possibly out of spec, these are taken back to the workshop for calibration. (We actually get a company called 'scaleways' in to do these calibrations for us, but you can do it yourself if you have the calibration weights)

Hope this is helpful,
Edwin.

Thanks GK and Edwin,

I appreciate your responses. In fact, I received a feedback from Seca, Germany regarding weighing scale calibration. We need to use atleast 2/3 of maximum weighing capacity of the scale. For example, if the scale could weigh a maximum of 150kg then the maximum weight used for calibration would be around 100kg. Therefore, one could choose 20, 40, 60, 80, 100kg weights for linearity and accuracy study. We have already implemented a form for recording atleast 4 -5 different readings with different weights.

Only lifting that much weight would be a problem for BME/BMRTs .

Edwin's suggestion is a good one but carrying the calibrated weighing scale from one place to another would be a cumbersome job but still better than lifting weights.

Now, the question is how to carry weights around the hospital to calibrate bariatric bed scales which weigh obese patients between 150 - 250kg .

Let us see how we perform our calibration in our forthcoming PPM on weighing scales and rely our experience to you.

Cheers
SEN

One or two technicians previously weighed on a set of accurate scales makes an easy to move and portable test weight for larger scales.
Weight yourself or even two people on a known set of scales then walk around the hospital, but not too fast so you sweat and do not eat, drink or go to the toilet. Then double check your weight on your return to the workshop.
Two large or three small people wil do for bariatric beds scales.
Robert

Why not move the scales to the workshop where the weights are?

We always used to carry around empty plastic containers, to be filled with a known volume of water at each site. Can be as precise as you choose to make it. You know, using the well-known relationship between litres of water and kilograms.

What do the weighing-scales companies do then?

I have seen hoists tested to large loads, as much as a bariatric bed scales would require. This was done with a hand pumped hydraulic plunger pulling down on the hoist through a calibrated electronic strain gauge. Could a frame be used that goes under the scales and a hydraulic ram presses down on the scale foot plate through an electronic strain guage? This could be quite portable and lighter than a lot of weights.
For ceiling hoists they carry around empty barrels and fill them with water. The easy part was filling them the hard part was finding a drain at floor level to empty them.
Obviously this does not help with beds but would it be possible to test the strain guage of the bed alone and then adding a calibration factor for the levers that actuate it?
When I had to check scales we had many smaller (10kg) weights, these were easy to move just a pain in the a**e (I mean back) lifting lots of weights on and off each time. But at least health and safety allowed us to do it.
Robert

Anyone applying this to their weighing scales?

http://www.medical-devices.gov.uk/mda/md...8B003E9065?OPEN

or search MHRA website under "weighing"

It would seem to specifically prohibit in-house calibration and repair of scales bought after Jan 2003 and might be considered to be a warning against such activities for scales bought before that date.

Any thoughts anyone?


Brian