# HP Forums

Full Version: (41) Brewing Calculations
You're currently viewing a stripped down version of our content. View the full version with proper formatting.
"MIX" calculates the amount of water for each of two temperatures to mix together to achieve a target volume and final temperature. Since brewing involves heating water it is often the case that one has heated the water too much and needs to cool it down to a specific temperature.

The program prompts for the following, enter the value and press R/S.
QTY Total: Enter the desired total volume of water.
TEMP HOT: Enter the temperature of the hot water.
TEMP COLD: Enter the temperature of the cold water.
TEMP FINAL: Enter the desired temperature after mixing the hot and cold water.

Note that this works for any system of units, F/C L/Gallons, as long as all entries are consistent.

The program first displays the amount of hot water, the user needs to press R/S to see the amount of cold water. The hot water volume is left in X and cold water volume is left in Y.
edit: fixed typo.
[attachment=5494]
(12-28-2017 04:38 AM)Craig Bladow Wrote: [ -> ]"MIX" calculates the amount of water for each of two temperatures to mix together to achieve a target volume and final temperature. Since brewing involves heating water it is often the case that one has heated the water too much and needs to cool it down to a specific temperature.

Looking at your program I remember a similar application in the photo lab: you have x milliliters of cold developer and want to dilute it with y milliliters of warm water to get a certain amount of working solution at a defined temperature.

Example: you have 100 ml of developer stock solution at 18 °C, and you want to dilute it 1:3 to get 400 ml at 20 °C. So you add 300 ml of 20,7 °C warm water.

What about a program that can handle either case? Or even any possible case? But this doesn't look trivial to me. ;-)

Finally, here is a text version of your program. I have taken the liberty of adding question marks at the prompts, omitting R04 (which is not required) and saving a line in the final calculation steps. I hope this is OK.

Code:
```LBL "MIX" "QTY TOTAL?" PROMPT STO 01 "TEMP HOT?" PROMPT STO 02 "TEMP COLD?" PROMPT STO 03 "TEMP FINAL?" PROMPT RCL 02 - RCL 01 * RCL 03 RCL 02 - / RCL 01 X<>Y - LASTX "QTY HOT " FIX 2 ARCL X AVIEW STOP "QTY CLD " ARCL Y FIX 4 AVIEW END```

Edit: saved another step during the calculation.

Dieter
Thanks Dieter! I attempted to OCR the listing but was not successful, not even close.

This will work for any liquid, so long as the it is the same liquid (or same heat capacity because it cancels out in the same liquid case) being mixed together. If the developer and water have different heat capacities then those need to be factored in.
(12-28-2017 10:07 PM)Craig Bladow Wrote: [ -> ]Thanks Dieter! I attempted to OCR the listing but was not successful, not even close.

Typing the listing by hand was probably faster than scanning and starting some kind of OCR software. ;-)

(12-28-2017 10:07 PM)Craig Bladow Wrote: [ -> ]This will work for any liquid, so long as the it is the same liquid (or same heat capacity because it cancels out in the same liquid case) being mixed together. If the developer and water have different heat capacities then those need to be factored in.

OK, I never thought about this. So obviously the heat capacities of water and common b&w developers are very close. #-)

Dieter
I had occasion to use this today an found the hot/cold results were reversed.

Code:
```LBL MIX "QTY TOTAL?" PROMPT STO 01 "TEMP HOT?" PROMPT STO 02 "TEMP COLD?" PROMPT STO 03 "TEMP FINAL?" PROMPT RCL 02 - RCL 01 * RCL 03 RCL 02 - / RCL 01 X<>Y - LASTX "QTY HOT " FIX 02 ARCL Y AVIEW STOP "QTY COLD " ARCL X FIX 04 AVIEW END```
Reference URL's
• HP Forums: https://www.hpmuseum.org/forum/index.php
• :