WSM Posted March 22, 2017 Posted March 22, 2017 (edited) Hi, I'm going to be adding a temperature display to my chlorate cell for its next run (May at the earliest). I bought an Inkbird ITC-100VH temperature controller/ display and a PT100 teflon insulated sensor online. I have 1/4" compression fittings, but the temperature sensor is too narrow to make a tight seal where it will enter the lid. The best solution I've come up with (Somewhat based on WSM's blog post I recall reading a while back) is to use a (roughly) 1/4" plastic plug with a hole drilled through the center for the sensor and then I'll use heat shrink tubing over them both to seal it. I have some NTE electronics brand clear, thin-walled heat shrink tubing on hand, but all it says is that it's polyolefin which, to the best of my knowledge, could be any of a number of different types of plastic. I tried contacting them to find out specifically which type it is, but, unsurprisingly, they didn't respond. Any idea if I can use this for my cell? I'm figuring I'll give it a try and if it doesn't hold up I'll purchase some better heat shrink tubing. Kevin Hi Kevin, What I did with the first sodium chlorate cell (last Summer), was to use a 1/4" PVDF compression fitting and filled the gaps with a slit piece of silicone tubing. When I tightened the ferrule, the silicone squeezed tight around the leads and sealed them. Say what you will but it worked. If you need to use shrink tube, use either PTFE or PVDF shrink tube, especially if it needs to come in contact with the electrolyte. It's available on eBay from China for a "reasonable" (some more than others) cost. It does require higher heat to shrink it, which may cause problems with lower melting point insulation on the sensor leads. With the PTFE coated PT100 sensors, I don't see a problem, but the split silicone tubing trick might be all you need to do to seal it in the compression fitting. One question though, are you using the temperature controller just as a temperature display or are you using it to control the temperature of your cell? Good luck and please share your experiences. WSM Edited March 22, 2017 by WSM
PTFE Posted March 22, 2017 Posted March 22, 2017 (edited) hey guys!For a Cell with a thin Cell material, you can use your sensor mounted at the outside, when you ensure its well insulated.Another good way is, to take a 10x8mm PTFE Tube and a 8x6mm Boro. Glass tube.A 5mm sensor will fit in well and with thermal sealing you can seal one side of your glass tube and putting it into the PTFE tube to make a thightly seal.Unfortunately i've only got one picture of it, since the small boro tube has broken when i disassembled the cell the last time.Between the right Cathode and the Anode you can see the small diffusor-tube for the HCL and in the front the Tube for the Temperatur sensor. Edited March 22, 2017 by PTFE
Kevin Posted March 27, 2017 Posted March 27, 2017 Hi Kevin, What I did with the first sodium chlorate cell (last Summer), was to use a 1/4" PVDF compression fitting and filled the gaps with a slit piece of silicone tubing. When I tightened the ferrule, the silicone squeezed tight around the leads and sealed them. Say what you will but it worked. If you need to use shrink tube, use either PTFE or PVDF shrink tube, especially if it needs to come in contact with the electrolyte. It's available on eBay from China for a "reasonable" (some more than others) cost. It does require higher heat to shrink it, which may cause problems with lower melting point insulation on the sensor leads. With the PTFE coated PT100 sensors, I don't see a problem, but the split silicone tubing trick might be all you need to do to seal it in the compression fitting. One question though, are you using the temperature controller just as a temperature display or are you using it to control the temperature of your cell? Good luck and please share your experiences. WSM I like that, it's really simple but would work quite nicely! Your idea also has me thinking.. To seal my lid I made my own silicone o-rings that fit into a groove in my lid like this: I made my o-ring by cutting a groove in HDPE plastic and filling it with silicone. Silicone doesn't bond to HDPE, so with some care I was able to remove it intact. I wonder if I could make a much smaller one and if it would work to seal my temperature sensor... I'll more than likely be using it just as a display initially and adjust things manually if I want to regulate the temperature. I did also purchased a solid-state relay that I may use to power a heating element if it's not running hot enough. However, these cells seem to run quite warm even without insulation, so if I decide to run it warmer I think I'd start with insulation. I may need to cool my cell rather than heat it so I might end up using my controller to operate a fan or small pump- though I'm not overly familiar with solid-state relays, so I'll have to read up on them first regarding their ability to operate inductive loads. I'm still fairly interested to know how well my heat shrink tubing will hold up to the conditions of the cell so I may involve some somewhere (even just around an electrode) to test it. hey guys!For a Cell with a thin Cell material, you can use your sensor mounted at the outside, when you ensure its well insulated.Another good way is, to take a 10x8mm PTFE Tube and a 8x6mm Boro. Glass tube.A 5mm sensor will fit in well and with thermal sealing you can seal one side of your glass tube and putting it into the PTFE tube to make a thightly seal.Unfortunately i've only got one picture of it, since the small boro tube has broken when i disassembled the cell the last time.Between the right Cathode and the Anode you can see the small diffusor-tube for the HCL and in the front the Tube for the Temperatur sensor. I placed a temperature sensor on the outside of my cell the last time I ran it. I didn't insulate it though, and once I thought of it I didn't want to because I figured it would render my initial temperature readings irrelevant. I may do it in the future though in case I want to know the temperature in multiple locations to see if the temperature is uniform. Did you get any salt creep coming through in between the boro. glass and the PTFE tubing? Thanks for the suggestions, WSM and PTFE, I'll be sure to post how things go! Kevin
WSM Posted March 27, 2017 Posted March 27, 2017 I like that, it's really simple but would work quite nicely! Your idea also has me thinking.. To seal my lid I made my own silicone o-rings that fit into a groove in my lid like this: I made my o-ring by cutting a groove in HDPE plastic and filling it with silicone. Silicone doesn't bond to HDPE, so with some care I was able to remove it intact. I wonder if I could make a much smaller one and if it would work to seal my temperature sensor... I'll more than likely be using it just as a display initially and adjust things manually if I want to regulate the temperature. I did also purchased a solid-state relay that I may use to power a heating element if it's not running hot enough. However, these cells seem to run quite warm even without insulation, so if I decide to run it warmer I think I'd start with insulation. I may need to cool my cell rather than heat it so I might end up using my controller to operate a fan or small pump- though I'm not overly familiar with solid-state relays, so I'll have to read up on them first regarding their ability to operate inductive loads. I'm still fairly interested to know how well my heat shrink tubing will hold up to the conditions of the cell so I may involve some somewhere (even just around an electrode) to test it. I placed a temperature sensor on the outside of my cell the last time I ran it. I didn't insulate it though, and once I thought of it I didn't want to because I figured it would render my initial temperature readings irrelevant. I may do it in the future though in case I want to know the temperature in multiple locations to see if the temperature is uniform.Did you get any salt creep coming through in between the boro. glass and the PTFE tubing? Thanks for the suggestions, WSM and PTFE, I'll be sure to post how things go!Kevin A problem with using a temperature controller on the cell, is it tends to control the temperature by switching the power supply off and on. During the off portion of the cycle, the electrolyte has a negative effect on the electrodes, causing them to break down. It's best to keep the power on continuously as the cell is running to prevent that break down and destruction of your electrodes. Solid state relays use a low voltage DC source to control a high voltage, high current AC load. A small, solid state controller can be used to operate heavy loads through the solid state relay (inductive, capacitive or resistive), if rated for the current draw of the load. Typically, the current draw of the load shouldn't be more than 80% of the rating of the relay (less is always okay). Good luck. WSM
WSM Posted March 27, 2017 Posted March 27, 2017 Sorry for the massive delay bit I have been busy with work.I only just got around to wiring up the whole system today.. Another reason for the delay is I decided I wanted the whole thing mounted on a wooden table that is dodgily made from a wooden pallet and sheets of thin plywood.There is also a dividing section that the ammeter sits in to seperate the electronics from the cell a little bit.Here is a pic from the electronics side. It is half wired together. I just took a closer look at the wiring setup. I forgot, is that the temperature meter or the power meter? WSM
greenlight Posted March 27, 2017 Posted March 27, 2017 (edited) Its a power meter that displays volts and amps WSM.It is nearly finished, I just have to make terminals for the electrodes again. Is something wrong with it? Edited March 27, 2017 by greenlight
Arthur Posted March 27, 2017 Posted March 27, 2017 Heat is generated by current in the effective resistance of the cell, heat goes out through the side walls of the cell. It's probably better to control the temperature by controlling the heat lost from the cell walls. Manually adding or removing blown air or insulating containers/foam sheet is my thought.
MrB Posted March 27, 2017 Posted March 27, 2017 Heat is generated by current in the effective resistance of the cell, heat goes out through the side walls of the cell. It's probably better to control the temperature by controlling the heat lost from the cell walls. Manually adding or removing blown air or insulating containers/foam sheet is my thought. Depending on how the cell is dimensioned, adding extra heating, or cooling, would probably be the smart way to control the temperature, yeah.B!
Arthur Posted March 27, 2017 Posted March 27, 2017 The electrodes in a chlorate cell don't do well with a big supply ripple. In a perc cell more than a few milli volts of ripple will kill a platinum electrode. Early commercial plants used big motor generator sets with six phase outputs so that the ripple after the rectifiers was minimised -when you had kilos of platinum at risk a little electrical engineering was well worth the cost!
WSM Posted March 27, 2017 Posted March 27, 2017 Its a power meter that displays volts and amps WSM.It is nearly finished, I just have to make terminals for the electrodes again. Is something wrong with it?No, it's fine. I would connect the voltage metering leads as close to thd cell as possible, for the most accurate voltage reads (what's actually getting to the electrodes). Keep up the good work. WSM
WSM Posted March 27, 2017 Posted March 27, 2017 (edited) Heat is generated by current in the effective resistance of the cell, heat goes out through the side walls of the cell. It's probably better to control the temperature by controlling the heat lost from the cell walls. Manually adding or removing blown air or insulating containers/foam sheet is my thought.I think that's right. If my cell is running too cool despite the heat it's generating, I'd add insulation to the cell outer wall. A fan may or may not cool it enough if it's running too hot. Industry usually cools their cells by pumping cooling water through piping running through the cathodes. An amateur cell is usually on a small enough scale that such extreme measures aren't required. WSM Edited March 30, 2017 by WSM
greenlight Posted March 28, 2017 Posted March 28, 2017 (edited) I just ran the system for the first time and it is reading unusually high on the amp meter. The volts are perfect as it is a 5 volt power supply but it is only 20 amp power supply?? Are the electrodes too close? Edited March 28, 2017 by greenlight
WSM Posted March 28, 2017 Posted March 28, 2017 I just ran the system for the first time and it is reading unusually high on the amp meter. The volts are perfect as it is a 5 volt power supply but it is only 20 amp power supply?? Are the electrodes too close?Check your wiring. I believe the shunt should be connected to the negative lead of the power supply. Also check the polarity of the sensor leads from the shunt to the meter. If all that checks out and the reads are still off, then I don't know. WSM
greenlight Posted March 29, 2017 Posted March 29, 2017 (edited) The shunt is connected to the negative lead from the power supply.I have uploaded a closer photo with the labeled positive and negative wires. Can you see anything wrong from the picture? Edited March 29, 2017 by greenlight
WSM Posted March 29, 2017 Posted March 29, 2017 (edited) The shunt is connected to the negative lead from the power supply.I have uploaded a closer photo with the labeled positive and negative wires. Can you see anything wrong from the picture? No, the shunt appears to wired correctly. What range meter do you have? I wonder if the shunt is matched to the meter (same current range as the meter)? WSM Edited March 29, 2017 by WSM
greenlight Posted March 29, 2017 Posted March 29, 2017 (edited) It has a maximum of 200 volt 200 amps. The shunt is a 20 amp shunt so that could be the problem.I have linked the ebay pages for the shunt and meter I purchased: http://m.ebay.com/itm/271808226092?_mwBanner=1 http://m.ebay.com/itm/DC-Current-Shunts-FOR-20A-50A-100A-200A-500A-Digital-LED-Voltmeter-Ammeter-/271729386459 Thankyou for all the help you have given so far:) Edited March 29, 2017 by greenlight
greenlight Posted March 29, 2017 Posted March 29, 2017 In the link for the meter it reads 0.00 for the amps. Mine doesn't have a decimal place it just reads 000....Maybe it is faulty meter otherwise?
WSM Posted March 29, 2017 Posted March 29, 2017 (edited) It has a maximum of 200 volt 200 amps. The shunt is a 20 amp shunt so that could be the problem.I have linked the ebay pages for the shunt and meter I purchased:http://m.ebay.com/itm/271808226092?_mwBanner=1http://m.ebay.com/itm/DC-Current-Shunts-FOR-20A-50A-100A-200A-500A-Digital-LED-Voltmeter-Ammeter-/271729386459Thankyou for all the help you have given so far:)I think that's the problem. The 200 Amp meter should be paired with the 200 Amp shunt. I don't believe the meter will be damaged by the low range shunt, but we'll see what it displays when the correct shunt is used. WSM Edited March 29, 2017 by WSM
greenlight Posted March 29, 2017 Posted March 29, 2017 Okay I will put one on order when I get paid and we will see where I am at when it is connected...Thanks again WSM
WSM Posted March 29, 2017 Posted March 29, 2017 (edited) Okay I will put one on order when I get paid and we will see where I am at when it is connected...Thanks again WSMYou're welcome, greenlight. I'm glad I could help. WSM Edit: Even though the range of the meter and shunt are 200 Amps, the readout will be accurate at the lower current levels. Edited March 29, 2017 by WSM
Arthur Posted March 29, 2017 Posted March 29, 2017 There are some DC clamp ammeters available, they are popular in auto electrical and solar power industries. Maybe you can buy or borrow one to check what your meter is reading.
Kevin Posted March 30, 2017 Posted March 30, 2017 It has a maximum of 200 volt 200 amps. The shunt is a 20 amp shunt so that could be the problem.I have linked the ebay pages for the shunt and meter I purchased: http://m.ebay.com/itm/271808226092?_mwBanner=1 http://m.ebay.com/itm/DC-Current-Shunts-FOR-20A-50A-100A-200A-500A-Digital-LED-Voltmeter-Ammeter-/271729386459 Thankyou for all the help you have given so far:) I think that's the problem. The 200 Amp meter should be paired with the 200 Amp shunt. I don't believe the meter will be damaged by the low range shunt, but we'll see what it displays when the correct shunt is used. WSM I believe WSM is correct. These meters actually measure the voltage drop across the shunt, which is a precise, low value resistor. If we use Ohm's law: V = IR where V = voltage, I = current, R = resistance, we can see that (with constant resistance) as the current increases, so does the voltage drop that your meter is reading. Current shunts tend to have a voltage drop of 75 mV when operating at their respective currents. For your 20A shunt to achieve a voltage drop of 75 mV, it would have a resistance of 3.75 mOhms (milli-ohms), whereas a 200A shunt would have a resistance of 0.375 mOhms. This means that your meter is operating off a shunt with 10x the resistance that it's calibrated at, which would mean the voltage drop across the shunt is 10x what it should be. In turn, this would be interpreted as 10x the current that is actually passing through your shunt. To put it simply: divide your meter's amp reading by 10 and you should be close to what your cell is actually operating at. Kevin
greenlight Posted March 31, 2017 Posted March 31, 2017 I will just order tge 200 amp shunt and it should work perfectly.
WSM Posted March 31, 2017 Posted March 31, 2017 I will just order tge 200 amp shunt and it should work perfectly.Yes, I believe so. WSM
WSM Posted March 31, 2017 Posted March 31, 2017 I've got two plans on my mind. First, I'm planning to continue work on the "high temperature" sodium chlorate cell, by sealing what appears to be a small leak in one of the electrodes. When the cell is proven "water-tight", the next step is to set it up and run it in the new configuration. The other plan is to publish more of the Homegrown Oxidizer articles in the blog section. I've submitted sixteen articles for publication in the PGI Bulletin, and want more of those available here. We'll see how far I can get in the next few days... WSM
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