• ### Organizing the build in a single place

Ahmed Hefnawi (Volta)11/25/2019 at 18:59 0 comments

Hello everyone,

I am trying to organize this build in a single place on my weblog and will be updating it regularly with more diagrams and eventually some Arduino/Teensy source code for data acquisition into the SD card.

Please let me know your thoughts on this post here: https://hefnawi.me/posts/custom-built-isothermal-calorimeter/

I would like to here your feedback as well as any suggestions you would like to know or read about this build.

Thank you very much,

Ahmed Hefnawi =)

• ### NaHCO3 Raw Readings

Ahmed Hefnawi (Volta)04/18/2015 at 20:04 0 comments

I added some NaHCO3 with water (exothermic reaction) into the sample vial and the reference vial contained sand at that time.

The following is a plot of the raw calorimeter readings in micro-Volts versus the time in seconds, the plot was created in Python using matplotlib.

I thought I should add the thermal power after conversion as well in milli-Watts,

• ### Calibration Results + Heat Equations

Ahmed Hefnawi (Volta)04/18/2015 at 02:41 0 comments

Calibration Coefficient as well as baseline was calculated using the calibration procedure explained in the previous log.

Next, I'll start calculating the heat of hydration for a cement sample with the help of a PhD student at my University.

Where,

U: Calorimeter Output in Volts (V)

P: Thermal Power in Watts (W)

Q: Heat Produced in Joules (J) or J/g

mc: Cement Weight in grams (g)

The duration of the experiment will be 3 days.

Also the calorimeter readings are logged every 5 seconds onto the microSD card.

• ### Calibrating the Calorimeter

Ahmed Hefnawi (Volta)04/08/2015 at 16:07 0 comments

It's time for calibrating the calorimeter! There are two parameters I'm interested in for the cement hydration process, which are:

• Calibration Coefficient
• Baseline

• ### Battery Power + PCB for Teensy 2.0

Ahmed Hefnawi (Volta)04/01/2015 at 22:02 1 comment

I'm busy at college so didn't have the chance to update the log much further.

I created a PCB to plug-in the Teensy 2.0 board and handle external power using a single cell 3.7V LiPo 4000mAh, running the Teensy at 3V instead of 5V will consume less power and give the battery roughly 6-8 days of continuous data logging to the SD card. During the experiment we experienced periodic loss of power so that's why we are adding external power source.

Also, I believe the battery powered device will reduce lots of the noise from the AC adapters.

I'll be adding more photos after I finish etching the board and soldering the components.

• ### Initial Prototype

Ahmed Hefnawi (Volta)03/17/2015 at 10:25 0 comments

The prototype is complete now, I calibrated my sensors with water in the reference vial so this calibration coefficient will work with solution but I will have to re-calibrate it for cement.

The calibration for cement will require filling the reference (inert) vial with Sand or NaCl. Because the specific heat capacity for water is 4182 J/kg while Concrete is 880 J/kg which matches that of Salt and NaCl of 880 J/kg. Sand will be accessible in our Lab, and its specific heat capacity is 830 J/kg.

A PhD student at my faculty is using the device now to perform the heat of hydration of cement experiment over an interval of 7 days. The data is being logged to a micro SD card into a CSV file every 5 seconds (which can be opened via libreOffice Calc or any spreadsheet program).

I'll be adding more specific details about the build and the calibration process.