Digital Scales: GemPro 500, AY123, Sartorius GD503
3-Way Comparison Test for Precision, Speed, Drift, Stability
This article first appeared in 2011.
JayChris, AccurateShooter.com’s IT “guru”, has tested three different digital scales. The first is the relatively inexpensive ($150.00) GemPro 500, the second was the $333.00 Sartorius AY123, which is very similar to the Denver Instrument MXX123 and Acculab-123. Lastly, JayChris tested his $1225.00 Sartorius GD503 lab scale. The 3-way comparison test produced interesting findings. We learned that the AY123 had some serious shortcomings when used to weigh powder. The GemPro 500 performed well for the price, but was quite a bit slower than the big GD503. In speed of response, accuracy of measurement, resistance to drift, and overall reliability, the GD503 was the clear winner in our comparison. Sometimes you do get what you pay for. CLICK HERE for GD503 Review with Videos.
BATTLE of the BALANCES
Three-Way Comparison Test: GemPro 500, Sartorius AY123, Sartorius GD503
Testing Report by JayChris
Precision Weighing Balances, www.balances.com, an authorized Sartorius Distributor, shipped me an AY123 (same as Denver MXX123, Acculab 123, etc.) along with a high-end GD503 force restoration scale. I had purchased the GD503, while the AY123 was a loaner for this comparison test. I included in this test a GemPro 500 scale that I already had. My key objective in this comparison test was to test each scale for measurement drift over time. We wanted to see if the displayed weight of a given object (here a certified test weight), would change over time, or with repeated measurements.
The first test was a “quick” test, where I measured the same weight ten (10) times, in the same order, about every 30 seconds or so. I did this at about the same speed as weighing out powder, maybe a bit slower. This took about 5 or 6 minutes. The second test was more-or-less an overnight test, where I measured the same weight in lengthening intervals, starting every 10 minutes, then every 30, then every 60, and so on. You can see the time series on the included graphs.
- I used the same 100 GRAM Sartorius certified check weight for every test (see photo). Note: 100 GRAMS = 1543.233 GRAINS
- I calibrated each scale within 30 seconds of each other before starting the test.
- I tare’d each scale within a few seconds of each other
- All three scales are connected to the same line conditioning PDU and are located in the same environment (right next to each other)
Measurement Resolution and Display Increments
- The Sartorius AY123 measures to the nearest hundredth of a grain (.00). Increments are in 0.02 grain divisions, i.e. the nearest two hundredth of a grain.
- The Sartorius GD503 measures to the nearest thousandth of a grain (.000). Increments are in 0.005 grain divisions, i.e. the nearest five thousandth of a grain.
- The GemPro 500 measures to the nearest half-tenth of a grain (.05).
NOTE: When weighing powder, I weigh to the nearest .05 grain so any of these provide adequate (or more-than) resolution.
FIRST SERIES Quick Test:
* X-axis is weighing series iteration
SECOND SERIES Time-based:
* X-axis is a time series in minutes-from-0.
THIRD SERIES AY123 “Stable” vs. “Unstable”:
* X-axis is a weighing series iteration
This is a test of the AY123 in “Stable” vs. “Unstable” environment mode. The GD503 was used for comparison. I ran this test to compare the AY123 in “Stable” conditions mode (default) vs. “Unstable” conditions mode, based on anecdotal reports that the “Unstable” mode produces more consistent results. I did not find that to be so. In addition, I found that the weighing time for the “Unstable” mode was extremely slow — taking nearly 5 – 7 seconds per instance to complete a measurement. It then takes a few seconds to return to zero. In the AY123′s default “Stable” mode, it takes a second or so. Based on my testing then, there is no advantage to running the AY123 (or similar clones) in the “unstable mood”. It will simply slow you down.
Observations and Conclusions
Overall, the GD503 was the most consistent, never varying more than .005 (five-thousandths) of a grain, which is about ten times less drift than the next closest scale. The GemPro was “close” behind, never varying more than .05 of a grain. The AY123 was consistently variable and lost significant resolution over time. It was difficult to plot the AY123 results because it rarely settled at a weight for longer than a few seconds — it would routinely come up with a different weight every few seconds, varying by as much as .04 of a grain. I selected the first reading it “settled” on as the “official” reading.
The one thing this test does NOT demonstrate is trickling — our previous Review of the GD503 has a video that shows that nicely. The GD503 gives you near instantaneous read-outs when trickling. By contrast, both the AY123 and GemPro 500 require a “trickle-and-wait-for-update” plan. The GD503 is really dramatically better in its ability to return a “final” weight very quickly. This allows efficient trickling. CLICK HERE for GD503 Review with Videos.
[UPDATE: One of our readers observed that there is a setting which can make the AY123 more responsive (and accurate) when trickling charges: "Note that the video shows the 123 jumping as powder is added. The reason is the scale is in the default setting, which is for single weightings. When changed to ‘Filling’ mode, the scale reacts very quickly, and in my case accurately. Trickling is easy in the ‘Filling’ mode. My experience is that the AY123 is an excellent scale, but is sensitive to environmental factors. The GD503 is way better and is also way more expensive." -- Matt P.]
GemPro 500 Performed Well — Drift Was Usually Minimal and Charges Settle Fairly Quickly
I’ve used the GemPro 500 for quite a while now and have found it to be fairly reliable. However, over one previous loading session I have seen it drift as much as .150 of a grain. I had to go back and re-weigh charges because of this. Therefore, I tend to tare it every five (5) weighings or so which is probably overkill based on one case. I’ve not had that problem since so I am guessing something happened environmentally (maybe I bumped it or something). Overall, the GemPro is not overly sensitive to environment and settles fairly quickly and reliably.
Charges Weighed by SD503 Have More Consistent Velocities, with lower SDs
I’ve loaded a few hundred rounds with the GD503 now. I have not found it to drift more than .010 of a grain in that time. So, now, I only tend to tare it once at the beginning of a load session. I have gotten extremely consistent velocities from charges loaded with this scale, with single-digit standard deviations. By contrast, previously, my best efforts usually resulted in standard deviations (SDs) in the low teens.
Based on my experience testing the AY123, I would not choose this scale to load powder with. The readings are just too variable. The slightest environment factors (breathing, hand movement, etc.) cause large changes in results. I tried to load some rounds using this scale (backed by my GD503 to verify) and I couldn’t do better than a few tenths of a grain, and that was with considerable effort. The Sartorius AY123 is really the wrong tool for the job when it comes to measuring powder.
Thanks to Precision Weighing Balances for providing the AY123 for comparison. The other two scales, the GemPro 500 and GD503, I purchased on my own nickel. [Editor's Note: When purchased in 2011, Jay's GD503 cost approximately $900.00. The current 2012 price at Balances.com is $1225.00.] All three of these digital scales can be purchased through the Precision Weighing Balances webstore: