JSN SR04T - Temperature Influencing Readings
-
@Timbergetter Isee you are still on 10us delay. I've read somewhere that 10us delay specified for the JSN is too short and causes failed readings in the JSN and I if I recall 15 or 20 us makes it more reliable. @zboblamont already mentioned this, so perhaps you already tried to increase the delay ???
Also, something else someone mentioned elsewhere was that metal casing caused some erratic readings on the JSN and grounding the case to the circuit's gnd helped.
@slt1 I can't recall where I read the 15 microsecond suggestion, but the spec sheet I found only states "a minimum of 10us".
The spec sheet I found was at https://www.jahankitshop.com/market/d/8946 . -
@slt1 I can't recall where I read the 15 microsecond suggestion, but the spec sheet I found only states "a minimum of 10us".
The spec sheet I found was at https://www.jahankitshop.com/market/d/8946 .@zboblamont Yes - that spec sheet does say "1,10uS above the TTL pulse". That is not a great english translation !
Chinglish translations sometimes might miss some important words - here is the spec translated by google from Chinese stating "above" 10us
Also, there are various people reporting issues at using 10 though. Here is something mentioned in the NewPing lib issues queue : https://bitbucket.org/teckel12/arduino-new-ping/issues/41/jsn-sr04t-20-needs-to-have-longer-high
-
@slt1 I can't recall where I read the 15 microsecond suggestion, but the spec sheet I found only states "a minimum of 10us".
The spec sheet I found was at https://www.jahankitshop.com/market/d/8946 .@zboblamont @slt1 It is my code that sets a sounding that is below 1300 µS to 1300 µS. The minimum depth that I end up reporting varies a little due to my temperature compensation but is nominally 0.22 m. I don’t know what the Newping library returns for these low and / or spurious soundings.
I have not tried pulse widths other than 10 µS yet because until recently the weather has been too cold for the spurious reading to occur (less than 13 ºC). It’s warmed up over the last day so the time is right now to try lengthening that pulse.
The only ground path to the metal box is via the ground side of the antenna fixed to the box. I’m not sure what alternate arrangement to try there.
I’ve got a few things to try now. I’m going to try being systematic, trying one thing at a time and observing the effect for a day or so. It could take a while especially if the weather doesn’t cooperate.
-
@zboblamont Yes - that spec sheet does say "1,10uS above the TTL pulse". That is not a great english translation !
Chinglish translations sometimes might miss some important words - here is the spec translated by google from Chinese stating "above" 10us
Also, there are various people reporting issues at using 10 though. Here is something mentioned in the NewPing lib issues queue : https://bitbucket.org/teckel12/arduino-new-ping/issues/41/jsn-sr04t-20-needs-to-have-longer-high
@slt1 It's a bit bass-ackward chinglish right enough, but what I took "above" to mean was greater than.
I tried using old and new ping to begin with, but couldn't get it to work, hence reversion to the manual method where I could try altering things (mostly blindly) in the absence of a spec. Some guy did a video on it saying don't buy this rubbish version 2.0, I'm sure the longer pulse was mentioned in the comments.
For some reason the problem JSN worked reliably on the sewage tank with a 5v setup, but when I extended the Trigger after reading about it, it found it started working on 3.3v. Unfortunately when the tank was emptied it began seeing ghost levels, so when next emptied I'll investigate further. If it isn't a head problem (have spare) then something is wrong with the board on QC. -
@zboblamont @slt1 It is my code that sets a sounding that is below 1300 µS to 1300 µS. The minimum depth that I end up reporting varies a little due to my temperature compensation but is nominally 0.22 m. I don’t know what the Newping library returns for these low and / or spurious soundings.
I have not tried pulse widths other than 10 µS yet because until recently the weather has been too cold for the spurious reading to occur (less than 13 ºC). It’s warmed up over the last day so the time is right now to try lengthening that pulse.
The only ground path to the metal box is via the ground side of the antenna fixed to the box. I’m not sure what alternate arrangement to try there.
I’ve got a few things to try now. I’m going to try being systematic, trying one thing at a time and observing the effect for a day or so. It could take a while especially if the weather doesn’t cooperate.
@timbergetter Fair enough, it's a puzzle but do report back with the fix, somebody will be along with a similar problem at some point.
The 10µs does seem to be an issue, perhaps that might be your first mod when the problem recurs.
As I'm resolving depths to the nearest mm within the permissible range rather than examining flight time, possibly I've a greater chance of getting consecutive readings due to arithmetic rounding down.
For a direct earth you would need to drill the box or lid and use a bolt I suspect, unless there are tapped collars inside. -
@timbergetter Fair enough, it's a puzzle but do report back with the fix, somebody will be along with a similar problem at some point.
The 10µs does seem to be an issue, perhaps that might be your first mod when the problem recurs.
As I'm resolving depths to the nearest mm within the permissible range rather than examining flight time, possibly I've a greater chance of getting consecutive readings due to arithmetic rounding down.
For a direct earth you would need to drill the box or lid and use a bolt I suspect, unless there are tapped collars inside.Have you guys considered using a US-100 ultrasonic sensor instead?
It can be used in the usual "ping" method, or in serial mode, in which case you can also get a reading from the built-in temperature sensor, and the distance measurement is automatically temperature compensated.
And it also works reliably at 3V.
I was using it for a year without problems in an diesel tank, and made the mistake to replace it with a TOF sensor. Now I'm back to the old reliable US-100. -
@slt1 It's a bit bass-ackward chinglish right enough, but what I took "above" to mean was greater than.
I tried using old and new ping to begin with, but couldn't get it to work, hence reversion to the manual method where I could try altering things (mostly blindly) in the absence of a spec. Some guy did a video on it saying don't buy this rubbish version 2.0, I'm sure the longer pulse was mentioned in the comments.
For some reason the problem JSN worked reliably on the sewage tank with a 5v setup, but when I extended the Trigger after reading about it, it found it started working on 3.3v. Unfortunately when the tank was emptied it began seeing ghost levels, so when next emptied I'll investigate further. If it isn't a head problem (have spare) then something is wrong with the board on QC. -
@zboblamont Are you "ghost levels" not perhaps echoes bouncing around the tank and nothing in the tank to absorb the sound quickly. If so perhaps increasing time between pings might help to let the previous ping dissipate.
@slt1 Nope. It is not a physical intrusion or an echo off the clean vertical sides, had to re-read notes until the penny dropped as there is a lot of nonsense in circulation.
A US pulse will decay quickly even in an echo chamber, but a first pulse in silence can only return by the shortest route, any echoes thereafter have no effect. You can calculate the decay for the frequency but it is miniscule. This is a board/head problem not an environmental one, but to summarise the iterations:
1 - 5v promini and separate battery pack passing info to Node over I2C. Perfect aside battery decay.
2 - Run JSN on a booster off Node battery with the Node using Trig and Echo via level converter, worked perfectly until I emptied the tank..
3 - Extended the Trig pulse and run on 3v3 direct, again no problem, until I emptied the tank.
Iterations 2 and 3 are hitting the same ghosts only when the tank is <50%, but crucially only on one board of two identical installs. The second in the Raw Water tank has worked perfectly on 3v3 down to empty and the tank has ribbed sides with ledges which might give reflections.
Have a spare head and 5v and 3v3 arduinos to trial when tank is emptied ca 3 weeks. Might buy another JSN and take pot luck, but not exactly confidently. -
Have you guys considered using a US-100 ultrasonic sensor instead?
It can be used in the usual "ping" method, or in serial mode, in which case you can also get a reading from the built-in temperature sensor, and the distance measurement is automatically temperature compensated.
And it also works reliably at 3V.
I was using it for a year without problems in an diesel tank, and made the mistake to replace it with a TOF sensor. Now I'm back to the old reliable US-100.@kted This is a standard type two diaphragm as @slt1 used, but as my tanks are sealed and underground the 100% humidity would kill them fairly quickly. There is no advantage over the button head in terms of accuracy, the button type allows the Node to be distant from the measuring point and are waterproof.
Most of these US can be operated in various modes by changing the value of one of the resistors, but not all can be operated down to 3v... -
I'm having the same / a simular issue of temperature related readings, but at a different temperature level (for me it must be > 14 degree). I massure the dew point as well (temperature = orange, dew point = yellow). It looks to be more related to water in the air than only to temperature.
@zboblamont have you been finally been able to find a solution?
