We believe that there are a few dos and don’ts every reloader should be aware of when using and buying an electronic reloading scale. Because many reloaders aren’t aware of the things that affect electronic reloading scale accuracy, they assume that the problem is with the scale. Here’s our dos and don’ts to ensure that you get the most accurate reading from your reloading scale.
7 Dos and don’ts for electronic reloading scales
- Do not rely on any scale with a minimum reading/resolution of 0.1 grain if you intend to achieve small variations in muzzle velocity. A resolution of 0.01 grain should be the norm.
- Try not to trickle slowly onto electronic scales because the reading will become inaccurate. If granules are dropped one by one onto the scale, reading deviations will become corrupt and the weight may be incorrect by more than 0.1 grain. Read below how to counter this problem
- Some electronic scales are influenced by mobile phone radiation. Place your mobile phone at least 7 feet away from your scale.
- All scales are influenced by electrical fields and electrical wires close by. Try to keep your mechanical balancing scale as well as your electronic scale far away from electrical appliances with strong magnetic fields.
- Calibrate and zero the electronic scale often. You will learn very quickly how often it is needed to maintain good reliability.
- If you need to slowly add granules, do so away from the scale. Always ensure the scale is reading a proper zero and add the complete powder charge in one go. This may sound like a lengthy process but it is much more reliable.
- Don’t press down on the weighting pad with your hand. The sensitive electronics can be damaged quite easily.
More about the inner workings of Electronic Reloading Scales
Often there are heavy debates about metering propellant by volume vs weight. This article is more about inaccuracies encountered in weighing a particular propellant charge with an electronic scale. It is quite possible that advocates for volume charging may have had bad experiences with accurate weighing knowingly or unknowingly. Recently I was incredibly frustrated with my mechanical balancing scale from a very reputable manufacturer. Needless to say this carried over to the target range with muzzle velocity variation outside 30fps and in the process a lot of time and money wasted.
My very first and obvious thought was to look for a more accurate scale. Mechanical balancing scales that can measure better than 0.02 grain simply does not exist and electronic was the logical alternative. The average gun shop offer only balancing scales and electronic powder dispensers with built in electronic scales and a resolution of 0.1 grain. Since I did have an electronic dispenser the first foolish plan was to rely on both scales to double check each charge. In my career as a MechanicalEngineer I’ve had many dealings with colleagues in the electronics field of expertise. Needles to say that the dark art of electronics let me down more often than not. Armed with a lot of knowledge of the inner workings of scales I set out to test the scale of my automatic powder dispenser.
Here is how the test was done. Switch the scale on and allow it to go though the start-up process. Calibrate for safety and make sure the scale read zero. Take about 30 granules and drop them one by one with tweezers onto the scale. For this test each granule measured about 0.02 grain. Do this fairly slowly by pausing a few seconds between placing each granule. Placing 30 granules adds up to about 0.6 grain. On my scale the reading was zero during the whole process. I then emptied all thirty granules in one throw and all of a sudden the scale reading was -0.4 grains. Calibrate the scale to zero and throw all 30 granules at once on the scale. The reading all of a sudden is 0.5 to 0.6 grain. This is what the article is all about. An apparent impossibility of electronic scales to correctly read a very slow increase in weight. It is risky to use a trickler directly on an electronic scale.
Most electronic scales have built in software to improve accuracy. Here is how they do it. First of all the technology of “strain gauges” is used to measure the deflection of a slender “spring metal” beam and this is converted to mass in grains, grams, kilograms and tonnages. Strain gauges generate a very minute signal based on the change of the resistance wire under load and due to its construction. Massive amplification is needed electronically before the strain gauge signal can be translated to a meaningful reading. In this amplification lies the problem since a lot of electronic noise is generated with huge amplification or gains. To improve the overall performance of the noise in the circuitry, software is used to logically filter or remove the noise, especially on scales used for very minute readings such as 0.01 grams or 0.1 grains. The creators of electronic scales rely on the logic assumption that if the weight does not change the reading must not change. To do this they have to assume that small increments over time is noise or interference and therefore the software should ignore/filter this and keep the reading constant. This is most likely why adding granules one by one with a time interval, is filtered as noised in such a way that the reading becomes totally inaccurate.
In short, the automatic dispenser scale even from a reputable manufacturer is not ideal for accurate measuring. Use it only for robust measurements and then follow it up with an accurate weight measurement on a precise instrument. With some help from friends I found a decently priced “stand alone” electronic scale with a resolution of 0.01 grain. With the Somchem propellant S335 in single granules at approximately 0.02 grain and with a new scale capable to read in 0.01 grain intervals my problems were mostly over. Fortunately the ability of the scale to identify single granules was found to be a substantial improvement. In some cases the placement of one or two granules were still not reflected accurately. At least with the dedicated scale the margin of error is much smaller and with a little care all my problems went away as the performance of the electronic scale is superior to the mechanical balancing scale. With this scale and revised procedures it is possible to improve muzzle velocity variation consistently to less then 15fps and mostly below 10fps.