why do my scales read negative????

[mtnman31]

Two suggestions if you aren't already doing so.
First, if you aren't already using one, maybe try powering it through a Uninteruptable Power Supply (UPS). I have a smaller UPS that was not being used and run my FX-120 scale through it. The UPS will help clean up and stabilize the power coming from the outlet. Keep your other electronics out of the room when you are working, i.e. cell phone, tablet, etc. The signals they use can also interfere with the more sensitive scales.

Second, make sure what ever your scale is sitting on is stable. I've got mine on a separate bench from the one my press is on. I also put a chunk of granite under it. The granite was a piece leftover from a counter install.

 

[JFrank]

The OP probably has it figured out by now.

 

[mtnman31]

lol, the curse of the dead thread strikes again.

 

[okie]

I had some too years back.... stamped on the pennyweights along with some centrifugal investment casting related gear.

yeah we had to use it in school. was pricey for broke kid...

 

[rardoin]

yeah we had to use it in school. was pricey for broke kid...

Yep, me too. I spent more time casting jewelry for my wife than using it for the intended purpose.

 

[rogn]

An observation that had me scrathing my head for a bit. My beam scale was drifting but my Dillon was just as stabile as ever. Ha dme worried until I realized that a small box I had placed on the table on the other side of the loading room was deflecting the air from the A/C and was forming eddies around the shelf the balance is on(eye level). The Dillon is on the bench and my body was blocking and odd air currents from affecting it. Move the boxing and life went back to normal.
The normal heat and A/C dynamics in the room are not usually affecting operation of the units.

 

[okie]

Yep, me too. I spent more time casting jewelry for my wife than using it for the intended purpose.

where did you go to school? Is LSU the only one there?

 

[338 dude]

How do I allow myself to get sucked into the crap!.....
am I the only one that just noticed this thread is 13 years old?!.....
Wayne

Not just you it happens

 

[NorCalMikie]

My RCBS 505 doesn't read negative. And it doesn't drift either.

 

[Coyotefurharvester]

I know this is old, static electricity can charge surfaces. That charge can become a force component. If you suspect your environmental conditions are producing static, a grounding strap can reduce the transfer.

 

[ronemus]

I worked daily with precision analytical balances (I'm a research chemist) that offer the precision and resolution we're looking for here, but those instruments cost thousands to tens of thousands of dollars. To reach a price we're willing to pay, some corners must be cut (vendors won't line up to sell to us below cost). Unfortunately, the instruction manuals accompanying our scales generally aren't very good at spelling out the steps necessary to have then operate to our satisfaction.

For stable zeros it's necessary to warm up for at least a few hours (they're generally left on continuously to avoid drift) and keep the room temperature fairly constant (within a few degrees).

Inexpensive scales such as these are commonly bothered by power line noise and transients, but those can be eliminated by using a filtered power strip; I use and recommend a Tripp-Lite Isobar.

Static electricity can easily shift readings by a few grains, so it pays to wipe down all plastic surfaces with an antistatic such as a drier sheet. Don't wear nylon or other static-prone fabrics when working with the scale. A humidifier set to maintain 35% RH will help a lot.

It is necessary to isolate the scale from drafts and vibrations. Laboratory scales with this sort of resolution generally have a housing around the pan with sliding doors for access and vibration isolators in the feet. An air current that's not even perceptible can easily shift readings at the level of precision we're looking for, but opening and closing a door is a nuisance when you're trying to up the pace. I use a carboard file box (intended for archival document storage) with one end cut out placed over the scale. The side goes down so the box can be removed for filling with powder, etc. without disturbing the scale. I leave off the top (now facing forward) so I can work my Pact scale/dispenser and A&D fX-120i scale. With the bench closing the bottom and the box closing three sides and the top, air currents have a hard time getting to the scale.

Vibrations are another problem - you don't want to have heavy equipment operating nearby, or foot traffic on a residential floor. You can make a vibration isolator by putting a heavy plate (Steel, stone, concrete, etc. - I use a granite surface plate bought on sale from Enco) on a slab of soft foam, but it may not be effective; really good vibration isolators are expensive.