12 Tips for Electronic Powder Scale Accuracy
By Lee Love
Weighing powder charges requires as much care as throwing the charge. All your careful powder measure technique is useless if you can't weight it accurately. I finally saved up and bought an electronic powder scale thinking it would solve all my frustrations with using a balance beam scale. Well, actually, it did solve most of them. It certainly is faster, but it also brought a few new problems to the table ... umm, make that reloading bench.
1 - Stability & Vibration
The scale must be on a rock steady table. A table that wiggles just isn’t going to cut it. If your bench doesn’t have adjustable feet, place shims under the legs. Remember to protect your scale by taking it off the bench before hammering any shims into place.
Even if the table doesn't wiggle, vibrations through the table can effect measurements. If possible, move the scale to a separate table that is isolated from the press vibrations. If that is not possible, make sure that you aren’t doing anything else while weighing.
The press may not be the only source of vibrations. I've seen more than one or two reloading benches sharing a room with the clothes washer and dryer. The wife doing laundry while you are dialing in a powder weight is not a good idea. Just how you go about getting her cooperation on this is a whole other can of worms!
Analytical labs place their scales on heavy marble or granite tables. The mass of the stone slab absorbs vibration. But these are too large and expensive for the average reloading bench. I’ve also seen anti-vibration foam pads that you place under your scale to absorb vibrations. Before you buy one, just try an old mouse pad and see if it helps. I took both concepts, combined them, and designed my own anti-vibration pad. I took a brick, set it on an old mouse pad and placed my scale on top. It works and cost practically nothing.
2 - Leveling
I originally thought this would be the first and most critical step of this list. As it turns out, leveling is not as critical as I would have though with modern electronic powder scales. Most of them don’t even have adjustable leveling feet, just three or four fixed feet. If your bench is level enough that bullets aren’t constantly rolling off the edge, it is probably okay. But if you needed to shim the feet to make the bench stop rocking in Tip #1, you may as well take the time to level it while you are there.
If you do want to check that your scale is level, buy a small bubble level that you can place directly on the weighing pan. Make sure it is the right size to rest flat on the pan and that it doesn’t weigh more than your scale’s capacity. I bought a lightweight, plastic bubble level at Home Depot for less than three dollars. Leave the scale turned off while leveling.
3 – Batteries and AC Power
A weak battery can make an electronic powder scale give erroneous readings long before it ever goes dead or gives a low battery warning. I load a fresh battery (mine uses a single 9V battery) in my scale every six months or so and use the old battery for some other less critical application. Buy a good quality battery. This is not a place to use a cheap battery.
Don’t substitute one of the new lithium batteries if the recommended battery is an alkaline. This could actually damage the scale’s electronics if not designed for it. Additionally, the low battery indicator circuit is calibrated for the specific battery type. It may not warn you when the battery is low if you use something other than the recommended type.
If your scale came with an AC Adapter, by all means use it. It will allow you to leave the scale on for extended periods without worrying about the battery going dead in the middle of a reloading session.
4 – Warm-up time
Warm-up time can affect the scale's measurement stability. Some scales can take as long as 30 minutes to warm up to a stable internal temperature, especially if the room is unusually cold. With an AC powdered scale, you can just leave it on while you are making other preparations. If your scale has an Auto-Off feature, you may need to disable it or set it for a longer time if possible. Battery powered scales may not allow long warm-up periods especially if it is one that drains batteries quickly. In that case, allow 30 to 60 seconds warm up time, keep the room temperature as stable as possible before starting a reloading session and use the zero button before every weight measurement.
5 – Calibration
Those check weights that come with most scales aren't just for looks. Use them! I check my scale calibration every time I set up for a reloading session. It is a good way to tell if your scale has warmed up and is ready to use. You should also check calibration if the scale has been moved (like to your shooting buddy’s house), is being operating it at a significantly different temperature than when it was last calibrated, and after you change the battery. If you just bought a new scale, checking the calibration is the first thing you should do before using the scale. Perform the calibration procedure as described in the owner’s manual if the calibration is off.
6 – Air Currents
A few electronic scales come with a cover. On some of these, the cover isn't just to keep dust off when not in use. Some covers are designed to be used during measurements and provide a valuable function by blocking air currents that can affect accuracy (the owners manual will tell you if your cover can be used during measurements).
If your scale doesn't have a cover designed for use during measurements, make sure it is located away from air currents in the room. Or, better yet, make an air current shield on three sides. I made one out of mat board (the stuff on which artists mount photographs). It is rigid, easy to cut with a utility or X-Acto knife, finished on both sides and available in lots of interesting colors. Foam core would work too. Either can be found at art & craft stores or even at Kinko’s. Make it tall enough to extend at least 3 inches above the weighing pan.
Adding a draft shield may not be enough. I had an air conditioning vent that blew in the direction of the reloading bench and the draft shield just didn't help enough. I finally found an inexpensive plastic deflector at the local hardware store that attached to the face of the wall vent and deflected the airflow away from the reloading bench. Simple, elegant, cheap .... and it worked!
7 – Static Electricity & Magnetic Fields
Static electricity near an electronic scale can affect measurement accuracy just as much as a stray air current. Always use a powder pan made from metal or from static dissipative plastic (e.g. the Lyman Powder Pal). PACT recommends washing their powder pan occasionally with soapy water and allowing the soap film to dry on the pan. The soap film helps dissipate static electricity. Keep any plastic materials away from the scale, including plastic loading blocks, die storage boxes, ammunition storage boxes, AkroBins, Styrofoam and vinyl. Keeping a clear space around the scale is generally a good practice anyway.
Don't forget the static on your body! Even though the days of the polyester leisure suit are (thankfully) long gone, you may have carpet under your reloading bench. I'm sure we've all scuffed our shoes across a carpet and then zapped some poor unsuspecting soul with a big arc of static electricity. Even if you don't build enough charge to cause a spark, you can build enough charge to affect your powder scale readings. A little anti-static laundry spray (Static Guard) applied to the carpet periodically is very effective.
Scales can be strongly affected by magnetic fields and electrical interference generated by electronic devices. Don't use a scale near any electronic device such as a computer, monitor, radio, or cell phone.
8 – Checking Zero
Use that zero button ... frequently! I always zero the scale immediately before every measurement. Some may feel this is overkill, but I feel it is worth the few extra seconds it takes to ensure the best measurement accuracy I can obtain from my scale.
9 – Center the Load
Place the load (powder pan, bullet, calibration weight, etc,) at the center of the weighing platform. Some powder scales have a cup shaped platform that automatically centers the powder pan. But if you are weighing a bullet, loaded cartridge or some other odd-shaped object, try to center it as best as possible.
10 - Cleanliness
Keep your scale clean. Dust and stray powder grains getting into the load cell can bind the mechanism. If your scale comes with a cover, keep it closed when you are not using the scale. The weighing platform can be removed on some scales so you can clean underneath. A soft artist’s paintbrush or a gentle puff of air is about all that should be needed to clean it. Whatever you do, don't flip your scale over and shake it to dislodge dust and powder grains. This could permanently damage the load cell.
11 – How NOT to break the Load Cell in your powder scale.
The “Load Cell” is the heart of every electronic scale. Lower priced scales usually use a strain gauge type load cell. Strain gauge load cells in particular, can be easily damaged if handled roughly.
• Never leave a load on a scale for an extended period of time as this can damage the load cell.
• Never place more weight on a scale than its uppermost limit. Overloading the scale can damage the load cell.
• Never drop anything on the weighing pan. Always place the load or calibration weight gently onto the scale. Dropping weight on the scale can damage the load cell, even if the weight is well below the scale’s uppermost limit.
If you ever do accidentally overload your scale, try recalibrating it. If the damage is slight, you may be able to save the scale.
12 – Read your Owner’s Manual
The owner’s manual for your scale is full of useful information specific to your scale. It may not be as exciting as a Tom Clancy techno-thriller, but it is worth reading.
These tips will get you a head start on accurate powder weighing and, hopefully, save you a few of the lessons I learned the hard way.
Source -- http://www.uniquetek.com
Rev. 1 - 09/19/05
By Lee Love
Weighing powder charges requires as much care as throwing the charge. All your careful powder measure technique is useless if you can't weight it accurately. I finally saved up and bought an electronic powder scale thinking it would solve all my frustrations with using a balance beam scale. Well, actually, it did solve most of them. It certainly is faster, but it also brought a few new problems to the table ... umm, make that reloading bench.
1 - Stability & Vibration
The scale must be on a rock steady table. A table that wiggles just isn’t going to cut it. If your bench doesn’t have adjustable feet, place shims under the legs. Remember to protect your scale by taking it off the bench before hammering any shims into place.
Even if the table doesn't wiggle, vibrations through the table can effect measurements. If possible, move the scale to a separate table that is isolated from the press vibrations. If that is not possible, make sure that you aren’t doing anything else while weighing.
The press may not be the only source of vibrations. I've seen more than one or two reloading benches sharing a room with the clothes washer and dryer. The wife doing laundry while you are dialing in a powder weight is not a good idea. Just how you go about getting her cooperation on this is a whole other can of worms!
Analytical labs place their scales on heavy marble or granite tables. The mass of the stone slab absorbs vibration. But these are too large and expensive for the average reloading bench. I’ve also seen anti-vibration foam pads that you place under your scale to absorb vibrations. Before you buy one, just try an old mouse pad and see if it helps. I took both concepts, combined them, and designed my own anti-vibration pad. I took a brick, set it on an old mouse pad and placed my scale on top. It works and cost practically nothing.
2 - Leveling
I originally thought this would be the first and most critical step of this list. As it turns out, leveling is not as critical as I would have though with modern electronic powder scales. Most of them don’t even have adjustable leveling feet, just three or four fixed feet. If your bench is level enough that bullets aren’t constantly rolling off the edge, it is probably okay. But if you needed to shim the feet to make the bench stop rocking in Tip #1, you may as well take the time to level it while you are there.
If you do want to check that your scale is level, buy a small bubble level that you can place directly on the weighing pan. Make sure it is the right size to rest flat on the pan and that it doesn’t weigh more than your scale’s capacity. I bought a lightweight, plastic bubble level at Home Depot for less than three dollars. Leave the scale turned off while leveling.
3 – Batteries and AC Power
A weak battery can make an electronic powder scale give erroneous readings long before it ever goes dead or gives a low battery warning. I load a fresh battery (mine uses a single 9V battery) in my scale every six months or so and use the old battery for some other less critical application. Buy a good quality battery. This is not a place to use a cheap battery.
Don’t substitute one of the new lithium batteries if the recommended battery is an alkaline. This could actually damage the scale’s electronics if not designed for it. Additionally, the low battery indicator circuit is calibrated for the specific battery type. It may not warn you when the battery is low if you use something other than the recommended type.
If your scale came with an AC Adapter, by all means use it. It will allow you to leave the scale on for extended periods without worrying about the battery going dead in the middle of a reloading session.
4 – Warm-up time
Warm-up time can affect the scale's measurement stability. Some scales can take as long as 30 minutes to warm up to a stable internal temperature, especially if the room is unusually cold. With an AC powdered scale, you can just leave it on while you are making other preparations. If your scale has an Auto-Off feature, you may need to disable it or set it for a longer time if possible. Battery powered scales may not allow long warm-up periods especially if it is one that drains batteries quickly. In that case, allow 30 to 60 seconds warm up time, keep the room temperature as stable as possible before starting a reloading session and use the zero button before every weight measurement.
5 – Calibration
Those check weights that come with most scales aren't just for looks. Use them! I check my scale calibration every time I set up for a reloading session. It is a good way to tell if your scale has warmed up and is ready to use. You should also check calibration if the scale has been moved (like to your shooting buddy’s house), is being operating it at a significantly different temperature than when it was last calibrated, and after you change the battery. If you just bought a new scale, checking the calibration is the first thing you should do before using the scale. Perform the calibration procedure as described in the owner’s manual if the calibration is off.
6 – Air Currents
A few electronic scales come with a cover. On some of these, the cover isn't just to keep dust off when not in use. Some covers are designed to be used during measurements and provide a valuable function by blocking air currents that can affect accuracy (the owners manual will tell you if your cover can be used during measurements).
If your scale doesn't have a cover designed for use during measurements, make sure it is located away from air currents in the room. Or, better yet, make an air current shield on three sides. I made one out of mat board (the stuff on which artists mount photographs). It is rigid, easy to cut with a utility or X-Acto knife, finished on both sides and available in lots of interesting colors. Foam core would work too. Either can be found at art & craft stores or even at Kinko’s. Make it tall enough to extend at least 3 inches above the weighing pan.
Adding a draft shield may not be enough. I had an air conditioning vent that blew in the direction of the reloading bench and the draft shield just didn't help enough. I finally found an inexpensive plastic deflector at the local hardware store that attached to the face of the wall vent and deflected the airflow away from the reloading bench. Simple, elegant, cheap .... and it worked!
7 – Static Electricity & Magnetic Fields
Static electricity near an electronic scale can affect measurement accuracy just as much as a stray air current. Always use a powder pan made from metal or from static dissipative plastic (e.g. the Lyman Powder Pal). PACT recommends washing their powder pan occasionally with soapy water and allowing the soap film to dry on the pan. The soap film helps dissipate static electricity. Keep any plastic materials away from the scale, including plastic loading blocks, die storage boxes, ammunition storage boxes, AkroBins, Styrofoam and vinyl. Keeping a clear space around the scale is generally a good practice anyway.
Don't forget the static on your body! Even though the days of the polyester leisure suit are (thankfully) long gone, you may have carpet under your reloading bench. I'm sure we've all scuffed our shoes across a carpet and then zapped some poor unsuspecting soul with a big arc of static electricity. Even if you don't build enough charge to cause a spark, you can build enough charge to affect your powder scale readings. A little anti-static laundry spray (Static Guard) applied to the carpet periodically is very effective.
Scales can be strongly affected by magnetic fields and electrical interference generated by electronic devices. Don't use a scale near any electronic device such as a computer, monitor, radio, or cell phone.
8 – Checking Zero
Use that zero button ... frequently! I always zero the scale immediately before every measurement. Some may feel this is overkill, but I feel it is worth the few extra seconds it takes to ensure the best measurement accuracy I can obtain from my scale.
9 – Center the Load
Place the load (powder pan, bullet, calibration weight, etc,) at the center of the weighing platform. Some powder scales have a cup shaped platform that automatically centers the powder pan. But if you are weighing a bullet, loaded cartridge or some other odd-shaped object, try to center it as best as possible.
10 - Cleanliness
Keep your scale clean. Dust and stray powder grains getting into the load cell can bind the mechanism. If your scale comes with a cover, keep it closed when you are not using the scale. The weighing platform can be removed on some scales so you can clean underneath. A soft artist’s paintbrush or a gentle puff of air is about all that should be needed to clean it. Whatever you do, don't flip your scale over and shake it to dislodge dust and powder grains. This could permanently damage the load cell.
11 – How NOT to break the Load Cell in your powder scale.
The “Load Cell” is the heart of every electronic scale. Lower priced scales usually use a strain gauge type load cell. Strain gauge load cells in particular, can be easily damaged if handled roughly.
• Never leave a load on a scale for an extended period of time as this can damage the load cell.
• Never place more weight on a scale than its uppermost limit. Overloading the scale can damage the load cell.
• Never drop anything on the weighing pan. Always place the load or calibration weight gently onto the scale. Dropping weight on the scale can damage the load cell, even if the weight is well below the scale’s uppermost limit.
If you ever do accidentally overload your scale, try recalibrating it. If the damage is slight, you may be able to save the scale.
12 – Read your Owner’s Manual
The owner’s manual for your scale is full of useful information specific to your scale. It may not be as exciting as a Tom Clancy techno-thriller, but it is worth reading.
These tips will get you a head start on accurate powder weighing and, hopefully, save you a few of the lessons I learned the hard way.
Source -- http://www.uniquetek.com
Rev. 1 - 09/19/05
