Can't Judge A Powder B

[chem_mom]

Has anyone tried putting together a conductivity tester using the instructions given on the CAJP wiki site? Is it necessary to solder the wires? Are the ready made testers working well? Thanks!!

[robotman]

The conductivity tester described in the wiki does indeed work. Soldering the connections is suggested, as it will make the connections more durable and precise, however not required. The main benefit for the one described in the wiki is it is fairly cheap to make, and easy to get done in a pinch.

Commercial Conductivity testers work great as well, this is the one I have seen used most often in CJAP. Flinn Conductivity Tester

[Skink]

My team assembled and tested one the other day. I recall commenting that it didn't look so great, but it works beautifully! They did note that they bought the best LED they could find, which may have an impact on performance. I would be interested in hearing if it does or not.

[chem_mom]

The conductivity tester described in the wiki does indeed work. Soldering the connections is suggested, as it will make the connections more durable and precise, however not required. The main benefit for the one described in the wiki is it is fairly cheap to make, and easy to get done in a pinch.

Commercial Conductivity testers work great as well, this is the one I have seen used most often in CJAP. Flinn Conductivity Tester

Thanks for the reply. We made our tester and it worked!! We twisted the wires round each other and used alligator clips for better connection. It sometimes falls apart so we will make some adjustments.

[knittingfrenzy18]

Just some suggestions for you all that are building your conductivity testers:

I went to the craft store and picked up a little wooden box with a hinged lid and a latch, and drilled some holes in the top and side. I taped the battery to the inside of the box, and glued the LED to a hole in the top (which let the leads through) and all the messy resistor + wiring and stuff is contained inside the box. Some longer wires protrude out the side of the box, and voila, a very concise, neat box with a switch (I decided to include one for safety measures to protect the LED), an LED, and some wires.

[ya5min88]

Do any of you have any useful suggestions for CJAP?

[Skink]

A good start might be determining exactly how to write your observations to shoot for five points. Do not use the 5-4-3-2-1 breakdown linked on the CJAP page of the National site, though! After that, find any powder and start practicing. I'd go as basic as sugar and, thereafter, choose something with a little more interesting chemistry.

[aparna123]

Does anyone know where I can buy a 9 volt digital conductivity meter? Thanks!

[computergeek3]

Does anyone know where I can buy a 9 volt digital conductivity meter? Thanks!

You could probably find a digital multimeter at your local hardware store, but those are too complex/can do too much/are too expensive for the purposes needed in this event.

I would look at the directions in the wiki and in this thread for how to build a fairly simple conductivity meter.

[dholdgreve]

Hmmm,
Went to my local radio shack last weekend for that exact purpose... They had no type of probes, no 9-volt battery caps, a whole drawer full of resistors, a whole drawer full of LEDs, and absolutely no help or expertise in pulling the thing together... Years ago, we used to be able to buy a totally self contained unit where the 9 volt battery just snapped onto the back end, but they no longer make them. There are several types available on ebay, but none that are powered by 9-volt batteries... most are powered by 2 of the 3 volt discs... Check clarifications... Those are not allowed, even though they are actually less voltage than what is allowed. Makes no sense to me, but those are the rules we must live with. In any case, after a 3-hour search, I finally found what I was looking for at Flynn Scientific, but they will only ship directly to schools, so I hope that's not a problem for you. Not cheap... they were over $20 each.