Indulging in resending, the original got mangled.
And I indeed forgot to mention the procedure assumes hitting tare before
removing
the measured
cup.
Suspicious of anything that could cause inaccuracies I have a measuring and
mixing
procedure
that many will probably consider overkill - do with it as you like.
For each cup I fill out an entry in each of the following 17 columns (assumes
4:1
ratio):
1. purpose of batch (rudderL, uni2)
2. date (20-11-02)
3. time (20:16)
4. temperature (23.8)
5. relative humidity (41)
6. zero reading (0.0)
7. 100g reading (100.0)
8. check zero (0.0)
9. cup reading (say 12.2)
10. tare reading (0.0)
11. resin1 reading (say 45.7)
12. hardener reading (say 57.7)
13. calculated resin2 reading (60.0)
14. actual resin2 reading (say 60.1)
15. calculated zero reading after tare (-72.3)
16. actual zero reading after tare (-72.3)
17. result (ok)
Notes:
Point 7: I use Satrue scales 200g, 0.1g resolution, comes with a 100g
calibration
weight.
Point 11 to 12: I use an "add hardener to read at least" table: 45.6 gives 57.0,
46.0 gives
57.5. etc.
Point 12 to 13: I use a household calculator ("add resin to exactly"):
(57.7-45.7)*5Point
14 to 15: household calculator ("minus final expected zero reading"):
60.1+12.2
Designed to achieve:
Resin first, for wetting cup walls.
Resin last to decrease pouring accuracy needed:
Hardener (point 12) within 0..+0.5g is ok.
Final resin (point 14) within -0.2..+0.2 is ok.
All the scales stability checking I could think of.
For point 16 I expect +-0.1g or better.
The measurement procedure takes about 1 minute.
Finally, I reuse my mixing stick. I wipe it at the end of a layup session and
save
it for the
next time. This avoids the possible influence of absorption (in an unwanted
ratio)
using new
sticks.
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