Single Banana pt1000 simulation - Help requested - Page 1
Forum section: electronics / general

author: itsbiodiversity
author_rank: Regular Contributor
timestamp: December 02, 2018, 04:50:26 pm
content: This may be basic, and I hope this is the right location for this question. I have a pH meter with automatic temperature compensation that I want to check the pt1000 temperature measurement function. There is only one single banana plug. What is the recommended way to connect the high and low from a resistance source to the single banana pt1000 input?

author: meeder
author_rank: Regular Contributor
timestamp: December 02, 2018, 04:56:32 pm
content: Does it have a single banana plug and a separate plug for the pH input?My guess would be that the other side of the pt1000 element is connected to the reference input of the pH input.You normally can't destroy it when wrongly connecting the pt1000.The accuracy of the temperature input isn't that critical anyway if it deviates by 1°C there isn't going to be an issue. The temperature compensation is only used to compensate for the change in slope of the pH sensitive glass, only in rare cases it is used for medium compensation besides the already mentioned compensation which is included in the Nernst equation.What kind of pH instrument are we talking about?

author: itsbiodiversity
author_rank: Regular Contributor
timestamp: December 02, 2018, 05:06:21 pm
content: It is a B30PCI from VWR. There is only one temperature compensation banana, while the pH probe has a female BNC connector. My other probes that I have used in the past do have one banana coming off of the bnc cable. The manual doesn't give the most information. I can try to dig up another probe I have in storage that does have the temperature cable, but I was hoping to simulate the values. I have a handheld resistance simulator and a clarostat decade box that I can get the 1000 ohms from. With all of this said - any idea? Worst case I use a probe with the single banana and measure temperature values, but simulating the entire range would be preferable.

author: meeder
author_rank: Regular Contributor
timestamp: December 02, 2018, 05:35:33 pm
content: You could easily check it with one side of the resistance simulator to the ATC socket and the other one to the reference socket which is above the BNC input.If that doesn't work you could try the shield of the BNC which would be normally connected internally to the reference input.I will see if I can do a quick check on my pH instrument to see if it works on that one. It is a different brand but they are normally connected in the same way between brands.

author: itsbiodiversity
author_rank: Regular Contributor
timestamp: December 02, 2018, 05:37:46 pm
content: the information is much appreciated. it says the reference sensor is for conductivity, but would that basically serve as the "ground"? I'll wait a little to see if you're able to dig one up before blasting the thing j/k j/k

author: itsbiodiversity
author_rank: Regular Contributor
timestamp: December 02, 2018, 05:39:12 pm
content: I also have a bnc to banana. Should I use the ground of the banana connected to the bnc (leaving the hi open) and the hi going to the ATC banana?

author: meeder
author_rank: Regular Contributor
timestamp: December 02, 2018, 05:42:06 pm
content: the pH input is a high impedance voltage measurement. The pH electrode generates a mV value following the Nernst equation.There is one additional input for the temperature so it needs to measure the resistance between that input and another input. My guess is the shield of the BNC since that is basically the ground of the measurement loop.You could measure the resistance between the shield of the BNC input and the separate reference input to see if they are connected internally.

author: itsbiodiversity
author_rank: Regular Contributor
timestamp: December 03, 2018, 01:43:03 pm
content: I just wanted to follow up: Meeder was correct. I connected the HI from RTD / source and the low to a bnc to banana splitter. Worked flawlessly with both an RTD sensor and simulator. Much appreciated.

author: meeder
author_rank: Regular Contributor
timestamp: December 03, 2018, 06:59:21 pm
content: Thanks for the follow-up!