I looked up the specs for that device. It's rated for 100PSI, which would correspond to about 230 feet of water, quite a lot of excess capacity for a tank under 4 feet tall.
I also note that the price generally seems to go up as the maximum pressure comes down, suggesting that anything close to the actual range needed would be quite costly.
I'm not familiar with the error being expressed in terms of full scale, but I believe that it means that the error rate is calculated at the extreme end of the scale and is constant over the entire range of readings.
This alarms me as the error is specified as 2%FS. Now, as I (think I) understand that expression, it means that at 100PSI, the measurement error is within +2 PSI and -2 PSI. Since the total expected range for the tank is 8'/(2.3PSI per foot) is about 3.5 PSI, so the error in reading may be on the order of >50% over the tank's estimated range of 0-3.5 PSI.
This seems horrific ! Can anybody tell me where my reasoning left the track and wandered off into the woods ?
Anything seems possible when you don't know what you're talking about.
That sensor seems a very promising possibility and well worth a good test if you have such a sensor to hand. Its a different sensor to the one in the Diyode Mag project. I see the Diyode one appears to be a well proven sensor used in agriculture, but I think that also applies to the sensor shown by @wamagee.
I looked up the specs for that device. It's rated for 100PSI, which would correspond to about 230 feet of water, quite a lot of excess capacity for a tank under 4 feet tall.
I also note that the price generally seems to go up as the maximum pressure comes down, suggesting that anything close to the actual range needed would be quite costly.
I'm not familiar with the error being expressed in terms of full scale, but I believe that it means that the error rate is calculated at the extreme end of the scale and is constant over the entire range of readings.
This alarms me as the error is specified as 2%FS. Now, as I (think I) understand that expression, it means that at 100PSI, the measurement error is within +2 PSI and -2 PSI. Since the total expected range for the tank is 8'/(2.3PSI per foot) is about 3.5 PSI, so the error in reading may be on the order of >50% over the tank's estimated range of 0-3.5 PSI.
This seems horrific ! Can anybody tell me where my reasoning left the track and wandered off into the woods ?
Sorry, that's a range of 4', not 8' so the range should be 4'/2.3 = 1.7 PSI which means that the error (+- 2PSI) could be in excess of the tank's capacity !!
Anything seems possible when you don't know what you're talking about.
I looked up the specs for that device. It's rated for 100PSI, which would correspond to about 230 feet of water, quite a lot of excess capacity for a tank under 4 feet tall.
I also note that the price generally seems to go up as the maximum pressure comes down, suggesting that anything close to the actual range needed would be quite costly.
I'm not familiar with the error being expressed in terms of full scale, but I believe that it means that the error rate is calculated at the extreme end of the scale and is constant over the entire range of readings.
This alarms me as the error is specified as 2%FS. Now, as I (think I) understand that expression, it means that at 100PSI, the measurement error is within +2 PSI and -2 PSI. Since the total expected range for the tank is 8'/(2.3PSI per foot) is about 3.5 PSI, so the error in reading may be on the order of >50% over the tank's estimated range of 0-3.5 PSI.
This seems horrific ! Can anybody tell me where my reasoning left the track and wandered off into the woods ?
The purpose I purchased the ones I have was to simply tell me if there is or is not pressure in the City and River water input lines. Don't care about anything else. As to putting them in the Measurement Stack to be used in calculating amount of water for sure they a a no go, thanks for your research effort!
That sensor seems a very promising possibility and well worth a good test if you have such a sensor to hand. Its a different sensor to the one in the Diyode Mag project. I see the Diyode one appears to be a well proven sensor used in agriculture, but I think that also applies to the sensor shown by @wamagee.
Sorry byron, so many sensors flying around today, which one are you talking about?
Sorry byron, so many sensors flying around today, which one are you talking about?
Its the sensor from the article where for the first attempt was to use an ultrasonic sensor, but this was abandoned due to ⅓ inaccurate readings. Instead to article goes on the show the use of :
Quote
The sensor uses the old but robust 4-20 mA current loop technology to report the measured pressure. When no water pressure is applied to the sensor, it will pass 4 mA of current, and when the sensor is at maximum range, it will pass 20 mA of current. A power source is needed to drive the sensor, and this is usually 24 VDC. Some sensors will pass 25 mA (or more) to indicate an error condition so the power supply must be capable of at least this range. These sensors are available to support various water depths and we chose the five-metre version as this was the best to suit our water depth of about two metres.
The 4-20 mA current loop technology is a very robust technology used widely in industrial automation. As it uses current rather than voltage, the cable length is not critical. Unlike voltage which drops off over distance, the current flowing around this circuit will be the same at any point in the loop.
End Quote
and goes on to show have to use a current shunt linked to an ADC chip to read a voltage to measure the water depth. I focused on the words 'old but robust' . And robust we like 😀
Sorry, that's a range of 4', not 8' so the range should be 4'/2.3 = 1.7 PSI which means that the error (+- 2PSI) could be in excess of the tank's capacity !!
For sure the pressure sensors I have are only useful for is there or is there not any pressure. Amount of pressure is not something I will use in the context of input water.
Its the sensor from the article where for the first attempt was to use an ultrasonic sensor, but this was abandoned due to ⅓ inaccurate readings. Instead to article goes on the show the use of :
Quote
The sensor uses the old but robust 4-20 mA current loop technology to report the measured pressure. When no water pressure is applied to the sensor, it will pass 4 mA of current, and when the sensor is at maximum range, it will pass 20 mA of current. A power source is needed to drive the sensor, and this is usually 24 VDC. Some sensors will pass 25 mA (or more) to indicate an error condition so the power supply must be capable of at least this range. These sensors are available to support various water depths and we chose the five-metre version as this was the best to suit our water depth of about two metres.
The 4-20 mA current loop technology is a very robust technology used widely in industrial automation. As it uses current rather than voltage, the cable length is not critical. Unlike voltage which drops off over distance, the current flowing around this circuit will be the same at any point in the loop.
End Quote
and goes on to show have to use a current shunt linked to an ADC chip to read a voltage to measure the water depth. I focused on the words 'old but robust' . And robust we like
Ok now I remember and will need to revisit. Head spinning!
This is a generic 24 VDC 4-20 mA submersible pressure sensor with a maximum depth of 5 metres. The sensor is mounted in a custom made stainless steel frame to orient it correctly in the bottom of the tank.
I purchased my sensor from eBay, model number 478526, and a label that states TL-MPM-70G, 0 ~ 5M, 4 ~ 20MA, 24 VDC.
According to the seller, the specifications include:
This is a generic 24 VDC 4-20 mA submersible pressure sensor with a maximum depth of 5 metres. The sensor is mounted in a custom made stainless steel frame to orient it correctly in the bottom of the tank.
I purchased my sensor from eBay, model number 478526, and a label that states TL-MPM-70G, 0 ~ 5M, 4 ~ 20MA, 24 VDC.
This might be the ticket. Only issue is it woks on pressure that might be affected by the pump running. BUT, that could be tested and if it is seriously affected then all meaningful measurements would be done with the pump off. Thanks!
This is a generic 24 VDC 4-20 mA submersible pressure sensor with a maximum depth of 5 metres. The sensor is mounted in a custom made stainless steel frame to orient it correctly in the bottom of the tank.
I purchased my sensor from eBay, model number 478526, and a label that states TL-MPM-70G, 0 ~ 5M, 4 ~ 20MA, 24 VDC.
I can't seem to find this exact part on Amazon (.com although it does appear on .ca), but it looks like comparable part would be:
This might be the ticket. Only issue is it woks on pressure that might be affected by the pump running. BUT, that could be tested and if it is seriously affected then all meaningful measurements would be done with the pump off. Thanks!
Does interference from the running pump really represent a major problem ?
From the discussions so far, it seems that we're leaning towards turning the pump on only when we've ascertained that we have enough water to finish the next zone. We'll take that reading before the pump starts, so that's not a problem.
It seems to me that the only potential problem is if there's a leak and the tank empties before the pump shuts off, thus overheating and possibly damaging the pump. Unless the sensor is so affected by the pump changing water pressure inside the tank that it causes the sensor to indicate that the tank still has water when, in fact, it's run dry; it doesn't seem to be serious.
Hopefully the backup system will prevent this from ever happening.
Anything seems possible when you don't know what you're talking about.
This sensor is sold under various brands by various firms. (The photo is identical on all offerings here on Amazon.) I have tried three brands, selecting only by price and delivery. We have 12 sensors installed measuring tank levels ranging from 8 to 26 feet in depth transmitting data to a PLC. We dropped them in the tank, filled them, then entered the empty and full readings as our scale. We now have fairly accurate depth measurements for each tank.
These units replaced FlowLine EchoPod Ultrasonic sensors that cost ten times the price. The EchoPods continued to throw false readings (empty or full) at apparently random times during the day. These have been solid.
The one page of instructions is in Chinese. However, the only item of interest is the photo showing the plus and negative wire. Any electronics tech will understand the obvious way to connect it.
I needed to remotely monitor the depth of water in a rain water catchment tank. This device allows me to do just that cheaply and simply. My setup used this device (0-3 meter version), a current to voltage converter (about $4 here on Amazon), an analog to digital voltage reader (ADS1115 type, about $5), and a raspberry pi. I was surprised how accurate of a reading I got with this device. I calibrated it using 12 inches of water, and it accurately read from 2 inches to 9 feet of water within 2% accuracy.
This is a spreadsheet that covers the range of my tank.
From this max error at 48" 122cm is 1.9" 4.9cm. This seems workable.
Manufacture states Measurement Accuracy: 0.5%FS
I don't know what FS means?
If you scroll down in any of these there is a Compare to similar products or products related to this item and there are links to the many more offerings of what appears to be the same product. Overall the ratings are very favorable with one very bad rating about no English instructions.
And likely I will need to test and come up with my own accuracy numbers.
Does interference from the running pump really represent a major problem ?
...
It seems to me that the only potential problem is if there's a leak and the tank empties before the pump shuts off, thus overheating and possibly damaging the pump.
My current pump setup has some type of pressure device following the pump and when there is no pressure/water for say 20 seconds it shuts off. This is managed through what the pump manufacturer calls a "Smart Box". This new system will need similar logic, for sure!
I was surprised how accurate of a reading I got with this device. I calibrated it using 12 inches of water, and it accurately read from 2 inches to 9 feet of water within 2% accuracy.
This is a spreadsheet that covers the range of my tank.
From this max error at 48" 122cm is 1.9" 4.9cm. This seems workable.
Manufacture states Measurement Accuracy: 0.5%FS
I don't know what FS means?
If you scroll down in any of these there is a Compare to similar products or products related to this item and there are links to the many more offerings of what appears to be the same product. Overall the ratings are very favorable with one very bad rating about no English instructions.
And likely I will need to test and come up with my own accuracy numbers.
That chart doesn't seem to give any actual measurements. The first two columns are heights in inches and centimetres, the second pair is just the first two columns with 2% added and the third pair is the first two with 2% subtracted. The final column is the difference between %2 and -2%.
There doesn't seem to be any real measured results displayed, so I don't think the chart is useful.
Also, the author doesn't know what FS means, so the origin of the 2% used as a range is somewhat questionable as well.
Anything seems possible when you don't know what you're talking about.
We use cookies on the DroneBot Workshop Forums to give you the most relevant experience by remembering your preferences and repeat visits. By clicking “Accept”, you consent to the use of ALL the cookies.
This website uses cookies to improve your experience while you navigate through the website. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. But opting out of some of these cookies may affect your browsing experience.
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.
Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website.
