From: gmk@falstaff.MAE.CWRU.EDU (Geoff Kotzar)
Subject: PACT Precision Powder Scale Review (LONG)
Organization: /etc/organization

The January issue of the Midway catalog now lists the
Pact Powder scale so I thought you might like some
impressions of the new PACT Digital Precision Powder
Scale after a week of use.

Let me start by saying that for a simple function scale
it is excellent, much better than the Dillon I purchased
a year ago and had to return, and I plan to keep it. But
it is not without some of its own problems.

The price of the unit is $149.95, and after adding shipping
& handling ($5.50) and the cash deduction ($3.89) which I
could not take having used a credit card and $0.66 for the
NRA the total came to $160. However, if you get it from
Midway you will only have to pay the $149.95 price tag; a
worthwhile savings.

GENERAL FEATURES:

When you open the shipping box you are greeted by four pieces
to documentation: an 8 page set of instructions, a single sheet
addendum, your invoice and a catalog of their timers and chronos.
The scale itself comes in a separate box which also contains
the A/C adapter. There is NO powder pan provided with this unit,
done intentionally. When I called PACT about this and a few other
things I was told that they expect you to be an experienced
reloader with one or more beam balances and therefore you would
already have a powder pan you could use. Talk about a lame, cheesy
excuse. Apparently, if you are a novice reloader they do not want
your business. I will get back to this a bit later.

The manual addendum sheet is intended to get you started just a
bit quicker than the manual. The manual itself is broken down into
the following sections:

Warranty Information
Introduction
Digital Scale Basics
Temperature Drift
Mechanical Drift
Shock
Improper Calibration
Scale Operation
Calibration
Tricks of the Trade

There is no list of specifications for the device however: like
linearity, repeatability, resolution or the maximum capacity of
the scale for example. This latter is especially significant since
load cell damage is specifically not covered by the warranty.
Midway does expressly state the capacity in their catalog, though.

For the record, the maximum capacity is 1500 grains and according
to the PACT rep I talked to there is a mechanical stop built in to
protect the loadcell from casual overloads.

The device operates on A/C only. There is no provision for battery
operation. The reason for this is that the loadcell is powered at
all times even though the display is off. This gets around the
delay due to self-heating induced thermal drift. The platten is
unlike all of their competitors' in that it is not a flat large
diameter unit on which the powder pan rests but rather a small
diameter cupped unit in which the powder pan, once you finally
get one, is cradled. If you plan to weigh a large number of, say,
bullets or cases, you will have to weigh them singly or make an
accessory platten out of some light material yourself and fit it to
the PACT platen. For my preliminary evaluation I used the top from
a pipe tobacco sample tin. It was large enough to fit over the pan
platten and shallow enough to not interfere with its operation. But
I plan to make a dedicated flat platten out of aluminum now that I
have decided to keep the scale.

It uses a four digit display and will represent the weight in grain
and gram mode. In grain mode, however, you get full resolution only
to weights of 999.9 grains, after that you only get full grain
increments. If you need the full resolution of the scale above 1000
grains, you have to switch to gram mode and convert back to grain
weight manually. This is a very minor inconvenience in my opinion.
It comes with two check weights, 20 and 50 gram, to provide a four
point calibration: 0, 20, 50 and 70 gram. These look for all the world
like Ohaus weights and the manual states that they are guaranteed
by their manufacturer to be accurate to +/- 1/10 of a grain.

There are four buttons on the face: ON/OFF, CAL/MENU, TARE/NO,
REVIEW/YES. Only the on/off, cal, tare, and review functions are
documented. In its present configuration, the REVIEW button changes
from grain to gram modes. The case has the display at an angle that
makes for very easy reading and the LCD display uses numbers 1/2" high.
The powder platten is left of center on the top while the power cord
inserts on the left side of the case. In keeping with the case
format of their timers, PACT has put the '57 Caddy fins on the
top running from the platten at an angle to the back edge of the
case. This combination of features makes using a powder dribbler,
this is a powder scale remember, a pain in the took-ass. If you
go to set in on the top of the case you have no flat surface
because of the fins. Set it off the left side and it gets tangled
with the power cord. By rights, because of the seismic sensitivity
of the unit, the dribbler is best kept off the case, but the power
plug could just as easily have inserted from the rear or the right
side which would have left a clear field for the powder dribbler.


PERFORMANCE:

I checked the accuracy using a set of Ohaus weights that had been
supplied with a piece of specialized test equipment from our lab.
These are nothing special and I would bet that they are just a super-
set of the check weight set supplied by RCBS. After performing a
calibration as described in the instructions I found some interesting
results.

APPLIED LOAD        MEASURED LOAD
 Gram/Grain          Gram/ Grain

  1 /  15.4          1.00/  15.5
  2 /  30.9          2.00/  30.9
  4 /  61.7          4.01/  61.8
  5 /  77.2          5.02/  77.5
  7 / 108.0          7.02/ 108.4
 10 / 154.3         10.02/ 154.6
 20 / 308.6         20.02/ 308.9
 30 / 463.0         30.02/ 463.3
 40 / 617.3         40.00/ 617.2
 50 / 771.6         49.98/ 771.2
 70 /1080.3         69.98/ 1080
 80 /1234.6         79.99/ 1234
 90 /1388.9         89.98/ 1389
100 /1543.2         99.99/ 1543
0.5 /   7.7          0.50/   7.7
0.3 /   4.6          0.30/   4.7
0.1 /   1.5          0.10/   1.6


To obtain the above data, I applied a load and toggled back
and forth between grain and gram modes to obtain both readings.
The Ohaus weights are supposed to be individually accurate to
+/- 0.01 grams (0.15 grains); the result of this is that any
applied load with more than a single weight could be more than
0.01 grams off from the nominal value. For example the 100 gram
applied load could actually be 100.04 on the high side to 99.96
on the low side since it required 4 of the weights to achieve
the 100 gram total. When in both grain and gram mode the readings
tracked the applied loads very well over the entire spectrum from
0.1 gram to 100 grams. The largest deviation from the "correct"
value was only 0.02 grams and given that the majority of the applied
loads required more than a single weight this deviation was within
the range I would expect. For the record the conversion factor they
use is 15.43 grains/gram, necessary for weights over 999.9 grains.
The unit is extremely repeatable as well, as the above test was
performed many times and the greatest deviation in the reading for
an applied weight was only 0.01 grams.

One more point about scale accuracy. IMHO, accuracy is nice but repeat-
ability (precision) is essential. If your scale is only slightly off,
say no more than 1/2 grain, as long as it is repeatable you can
still reload confidently. If the scale reads low, meaning that
your powder charges are heavier than you think, you can get
into trouble sooner than if it reads high. But if you follow
proper reloading practice and always work your loads up from
below, you won't run into any problems. The one nice thing about
scales that are accurate as well as repeatable is that you can
transfer loading operations across systems. A load that a friend
developed on his rig can be loaded on yours and will still be safe
in HIS firearms.

One of the best features of this unit is the auto-tare function.
There is a manual tare capability to allow the user to zero out
the weight of some reference container after performing a cali-
bration. Such containers could be a powder pan or a cartridge
case (as when determining the water capacity). Because of the
sensitivity to thermal changes, vibration and the like the zero
of the scale is constantly drifting and the device continually
corrects for such effects using the auto-tare function. The best
way to explain why the PACT inplementation is so good is to first
recount the problem I had with the Dillon scale I tried previously.

With the Dillon scale, when I tried to work up a load I dropped a
charge into the powder pan and then started to dribble the remaining
powder into the pan. The Dillon treated the slowy added weight as a
zero drift. It compensated for this "drift" by adding the small
detected weight increases to the tare value rather than to the
charge weight value. In one instance I found that I had added 2.8
grains more powder to the weighed charge than the scale indicated.
When that charge was transferred to the case and the pan returned
to the scale the "zero" reading was negative, by 2.8 grains. Re-
zeroing the pan and pouring the just-weighed charge back into the
pan showed that the actual weight was my desired 75 grains plus 2.8
additional grains of powder for a total of 77.8 grains. I verified
this with my beam balance as well. According to Dillon, this problem
has been corrected as of early in '93.

The nice features of this PACT unit are 1)that I was unable to trick
it into adding the small weight increases generated by dribbling pow-
der into pan to the tare value, 2)that the auto-tare has a warning
feature if the tare value drifts more than 0.5 grains (nominal) from
your last manually generated tare value, and 3)that the settling time
is very short and therefore you are less likely to get ahead of the
scale with your dribbling operation.

When the auto-tare function is in operation you are made aware of
it by the decimal point flashing. Also, when the unit is in the
process of detecting your added weight, the decimal point flashes.
The reading reaches a stable value after about 1.25 seconds as well
as I can detect, but the decimal point continues to flash for about
another 1.25 seconds. From what I could determine, after the first
1 1/4 seconds you can add additional weight and the scale will track
it accurately.

My unit did not perform its auto-tare operations exactly as claimed.
The 0.5 grain limit to the auto-tare means that it is incapable of
measuring weights less than that value: the unit automatically
re-zeros itself. My unit would re-zero itself without tripping
the warning feature with weights as large as 0.6 grains. My weight
set only had fractional weights down to 10 milligrams so I was
only able to check the auto-tare threshhold in 10 mg increments.
The 0.5 grain value is equal to 32.4 milligrams. I added weight to
the pan starting with 10 mg in 10 mg increments. When I got to 40 mg
the auto-tare warning had still not activated. When the next 10 mg
were added the warning went off: the word "tare" flashes alternately
with the weight on the display. So the conclusion is that with my unit
the auto-tare warning threshhold is somewhere between 0.6 and 0.8 grains.
For my applications, this is a trivial discrepancy.

One more point is the maximum capacity of the unit. I don't know just
when the mechanical stop is engaged but the display shows an error
message whenever the load exceeds 110 grams (1698 grains).


MAIN COMPLAINTS:

1) NO POWDER PAN: This one is infuriating, especially if you don't
   already have a beam balance to pilfer the powder pan from. As I
   said above, if you are a novice PACT does not want your business!
   Nowhere do they tell you that no powder pan is included, not in
   the ad that appeared in the Dec17 GunList, and other publications
   since then, and not in the Midway ad either. They do not even
   warn you of this if you place a phone order with them. I know
   this for a fact since that is exactly how I placed my order.
   The most that the SOB's can claim is that they do not show a
   powder pan in their advertisement. But their copy reads in part
   "Take a look at our platten design, its (sic) engineered to
   perfectly center the standard powder cup over...", which kind
   of implies that one comes standard with it. No?

   This is not an inconsequential problem either. Suppose you have one
   of these scales now but do not have a powder pan. Well you just order
   it from Midway, right? Wrong, Midway does not carry them. So where do
   you get one? I was able to find only four places that list them: RCBS,
   Huntington, Natchez Shooters Supply, and Lock, Stock and Barrel. The
   first three all charge between $12 and $13 for them and Natchez has a
   $35 minimum order. LS&B lists them for $8.50. When you add shipping to
   that you are looking at between $12 and $16 for the pan. Not to men-
   tion the added delay. My guess is that Midway will start carrying the
   pans soon, just because of this problem. PACT also should carry them
   as an accessory since they must really be sweating getting under the
   magic $150.00 mark.

2) INADEQUATE PLATTEN PROTECTION: PACT makes a point of telling the new
   owner in two locations in the instuction manual that damage to the
   loadcell is not covered under the "Lifetime Warranty". They list only
   one accessory and that is a dust cover, whether this is a hard
   cover or a soft one I cannot say since I did not order one. But
   because the loadcell is not covered by the warranty it demands
   some extra protection. Now back to my criticism of the '57 Caddy
   fins on the case top. If the fins were not there you could place
   a cup over the top of the platten to provide some protection to
   the platten and the laodcell. Better yet would be an annular ring
   molded into the top of the case onto which a plastic or metal cup
   could be snapped or screwed. This would provide much more positive
   protection for the loadcell because it would resist being dislodged.
   With the fins on the case, you can still place a cup over the top
   of the platten but it is not very secure and prone to sliding around.

   At this point, if you buy a new powder pan and the dust cover, assuming
   that it is a hard one and affords protection to the unwarrantied load-
   cell, you are looking at something around a $180 powder scale. Not
   quite the bargain it appears at first.


3) MANUAL OMISSIONS: By and large the instructions are very good. They
   provide the layman with an acceptable understanding of the sources
   of drift (thermal and mechanical) and the problem of transducer non-
   linearity. But as I said earlier, there are no specs provided, not
   even the most fundamental one of maximum capacity. This definitely
   needs to be corrected. Additionally, there is a feature claimed in
   the PACT advertisement that is not discussed in the instructions.
   The ad reads "In addition, our software allows you to add your own
   calibration points for further refinement." This is just not so.
   Either it was never implemented or it was not documented. But the
   fact is that you can only use a four point calibration at this time.


PACT has a FAX number which I have obtained (214-641-2641) and I am going
to send tham a copy of this so you can expect an update in the near future.
When I receive their response I will forward it to the group.


geoff kotzar

From: gmk@falstaff.MAE.CWRU.EDU (Geoff Kotzar)
Subject: Re: Any opinions on PACT electronic scale?
Organization: /etc/organization

In article <2qm2pd$45u@tadpole.fc.hp.com> bartb@hpfcla.fc.hp.com (Bart Bobbitt) writes:
#Yes.  Checked one out at a gun show recently.
#
#They were less repeatable than a cheap beam scale.  And were slower to use.
#A 40-grain bullet on it varied +/- .2 grains.
#
#BB


After reading this I went and checked mine out, because I do not recall
having anything like the problems listed here.

I ran four repeatability tests:

52gr Sierra Match HPBT and got   52.0 +/- 0.0 for n>20

155gr Sierra Match HPBT         154.9 +/- 0.0 for n>20

300gr Nosler Partition          300.5 +/- 0.0 for n>20

400gr Hornady RN                400.6 +0.1/-0.0 for n>10

My scale does have one quirk, though. It is somewhat position sensitive.
If the point load platten closest to the user is called 6 o'clock and the
point farthest away 12 o'clock, I got the following:

 52 gr: no position dependent error

155 gr: -0.1 @ 6 o'clock, 0.0 @ all other positions

300 gr: +0.2 @ 12 o'clock and -0.1 @ 6 o'clock, no error along 3-9 line

400 gr: +0.2 @ 12 o'clock and -0.2 @ 6 o'clock, no error along 3-9 line

The above are for the bullets placed no in the concave platten but on the
rim, to accentuate the effect. Thees errors were themselves very repeatable.
They were measured not less than 5 times each. If the above is not quite
clear, for the 300, for example, at 6 o'clock the reading would be 300.4,
or 0.1 less than the central reading; and, at 12 o'clock it would be 300.7,
or 0.2 more than the central reading. But this effect of position did not
vary, for n's > 5.

Now my loading bench, with all the reloading supplies, must weigh well
over 300 pounds so it is rather stable. I suspect that the effect Bart
is reporting my be due to the environment, especially air currents. If
I move around a lot after setting something on the pan, I have to give
the thing time to settle down. Otherwise, I get a reading that is diff-
erent than the final reading.

As far a settling times go, mine is slightly slower than my old Lyman
beam balance, but not enough to really be a hindrance. The Dillon I
tried was glacial by comparison.

geoff kotzar