Digital scale for the garage

I acquired a couple free 1980 vintage digital hanging scales (1999# capacity) a while back in hopes of using them in the garage. To my dismay, neither worked when I got them. (Okay, yeah, what did I expect for free.) I had some e-mail correspondences with the manufacturer's tech support, but all I received were perplexed replies. Apparently their tech support personnel were hired well after 1980, as I had to convince the rep that they actually manufactured the item I had on my work bench. So, after a lot of wasted effort there, my next move was to spend a bunch of time tracing the internal pcb wiring, measuring internal voltages, and popping a lot of internal fuses. Between finding and repairing some parts issues, and thankfully having a duplicate set of circuit boards to compare readings, I got one of them working.



These scales use a hanging load cell transducer.



The main reason I've been wanting to get one of these scales working is to weigh the current BB engine in the '69, and compare it to the engine currently under construction on my engine stand. I can just hook the load cell to my engine hoist, and then hook the chains to the bottom of the load cell. I've always heard estimates of what BB engines weigh, but now I'm hoping to get an actual measurement.
However, now that I've got the scale functioning, I need to calibrate it. I'm trying to figure out some loads to put on it to calibrate it (I'm thinking of some five gallon buckets filled with sand, and then weighed at a scale company to get an accurate weight for these loads). Other than that, anyone have some better ways to do this?

Thanks for any help on this.
Mike

Get some large can goods at the grocery , have them weighed individually at the meat counter and write their weight on them ,add them up. That should be pretty accurate. That way you can add and remove and see if changes in weight are recorded accurately by the scale.

Single point calibration?

Get a cheap mechanical bathroom scales with a 300lb capacity. Load it up with 250lbs of stuff in a box (as measured on the mechanical scale). Then lift the box with the load cell. The decrease in weight should be reflected in the digital scale.

BBShark said:

Single point calibration?

Get a cheap mechanical bathroom scales with a 300lb capacity. Load it up with 250lbs of stuff in a box (as measured on the mechanical scale). Then lift the box with the load cell. The decrease in weight should be reflected in the digital scale.

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I've got a couple of bathroom scales out in the garage that I can use for a test like this. My concern is I don't know how accurate my Walmart scales are at 250 pound readings. I suppose I could compare the readings from each scale (I don't know which one to trust if they're different, though). And, whatever error there is at 250 pounds will be multiplied by two when measuring a 500 pound weight/engine. That's why my original direction was to fabricate a large weight and get it accurately weighed at a scale company.

But, I think if I use your suggestion I can get the scale roughed in pretty damn close (at 250 or 500 pounds load), and then add the "canned good" weights that Roger suggested. The canned goods are a known good measurement, and I can see if the scale reading changes the same as the store scale. I believe this combination of techniques ought to work out quite well.

Thanks, guys. I do appreciate it!

Do you still have the H.F. scale , it will weigh a gallon jug at a time. I just filled one and it weighed 141.25 oz. Its supposed to handle 11lbs.,so 8 shouldn't hurt it.

Go to Walmart and pick up a scale in the bathroom department and then walk over to the sporting goods and put some freeweigh disks on it. Calibrate it and buy it.

I bought 4 cheap ones for a project I was working on and was shocked at how accurate they were.

Oh, after your done, take the scale back to Walmart and tell them you want your money back!

BBShark said:

Oh, after your done, take the scale back to Walmart and tell them you want your money back!

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Thrifty

DWncchs said:

Do you still have the H.F. scale , it will weigh a gallon jug at a time. I just filled one and it weighed 141.25 oz. Its supposed to handle 11lbs.,so 8 shouldn't hurt it.

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Yep, still have the scale. I had forgotten about it. We recently moved and I often forget where I put lotsa stuff.
Looks like I'll be able to fabricate the small-weight calibration samples in the garage instead and avoid annoying the meat counter manager. :amused:

How accurate are the weights that weight lifters use? Might be just what you need.

DC