Mongo Blongo
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Fixing Electronic Scale
My electronic scale seems to have a slight problem. It's an A&D HL-200, about 2 yrs old which reads to 0.1g and has a max weight of 200g.
It has always been treated with care and stays in it's original box when unused.
When I switch it on it is supposed to show all segments on the screen then "-------" on the screen while it is zeroing and then show
"0.0g", ready for weighing.
The problem is that it stays on the "-------" stage.
I found that if I then add a weight of approx 50g or more to it will change to show all segments again then "-------" and then it will show
"0.0g". I can then use it as if nothing was wrong, providing i leave the 50 g weight on it.
If I take the weight off it will read -50g and then it is not possible to zero it again.
I can only assume the top weighing platform is not exerting enough weight on the sensor to begin with.
If the removable top weighing platform is removed to reveal the platform under it you can see two screws next to each other on a small square plate
with Alan key fittings on the heads of the screws. These screws are situated on the left side of the platform. There is an identical set of screws on
the underside of the instrument.I have seen these on other scales before.
Are these screws used to tighten the platform onto the sensor? I do not want to mess with anything which could change the accuracy of the instrument
as it quite expensive. I also do not have calibration weights if anything goes wrong.
I have no idea what could have caused this problem.
If anyone here has seen this problem before or could give me any advice on this I would be very grateful.
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Marvin
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This sounds like a calibration problem. Check the manual or contact the manufacturer. I would not be inclined to alter anything physical until this
is ruled out.
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Mr. Wizard
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Checking the calibration is a great suggestion. Do you know the calibration procedure of your scale? Maybe you inadvertently started the procedure and
it is stuck in the process. If that isn't the problem, try removing the battery or power source and then put in a new battery. Check the
position of the platform on the scale, and make sure nothing has gotten underneath the platform, like a piece of foam packing, paper, or a bit of
trash. Picking the scale up by the platform may have moved it from the correct position, but it still looks right. Good luck
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Twospoons
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I know this sounds stupid and obvious, but my experiences in the PC repair industry leads me to ask : Have you checked / replaced the batteries? Have
you checked the battery connections for corrosion?
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Mongo Blongo
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Thanks for the advice guys. I use a mains power supply that seems to be working fine.
I have gone through the calibration for gravity acceleration which was correct at 9.789 (or something) for my area.
I have taken off the top half of the case to see where thoes screws go and they seem to fix the platform onto a "leaver sensor" so
tightening them up would do nothing to exert more pressure.
I have not yet tried calibration with a weight yet as I have none accurate enough.
I will try to contact the manufacturer before doing anything that could make the problem worse.
[Edited on 5-4-2005 by Mongo Blongo]
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