Bonjour,
Je souhaite raccorder deux sondes PT100 à une carte K8055.
Pouvez vous me conseiller sur la marche a suivre ?
Le k8067 ne conviens pas car mes températures vont de 10 à 110°C et les sondes doivent être étanche…
Merci d’avance pour votre aide,
Boris
Sorry that I answer in Enlish.
You can use Pt100 temperature sensor but the voltage span that you get from the sensor is rather low.
The resistance at 0°C is 100 ohms and at 110°C 142.29 ohms.
By using 1k ohm series resistor (from +5V of the card) to the Pt100 you get about 5mA current through the sensor. That is rather high and may cause some temperature rise of the Pt100 sensor. In the following table there are calculated the voltage over the Pt100 sensor at different temperatures.
By selecting proper value for the gain setting resistors R8 and R9 you get gain of 5 from the amplifier IC1A and IC1B. The voltage range to the AD converter and the output reading are calculated to the table:
[code]Temp Pt100 Pt100 amplified AD converter
°C ohms Voltage by 5 reading
0 100 0.45 2.27 116
10 103.9 0.47 2.35 120
20 107.79 0.49 2.43 124
30 111.67 0.50 2.51 128
40 115.54 0.52 2.59 132
50 119.4 0.53 2.67 136
60 123.24 0.55 2.74 140
70 127.08 0.56 2.82 144
80 130.9 0.58 2.89 148
90 134.71 0.59 2.97 151
100 138.51 0.61 3.04 155
110 142.29 0.62 3.11 159[/code]
Dans un process industriel, avec une gamme de température à mesurer de 14à 100°C, par quel type de sonde puis je remplacer mes PT100 pour avoir plus de precision ?
Boris
peut être que vous pouvez la remplacer par une sonde K (a confirmer) mais qui est moins précise. Par contre je ne connais pas les valeurs de résistance.
[quote=“VEL255”]…
You can use Pt100 temperature sensor but the voltage span that you get from the sensor is rather low.
The resistance at 0°C is 100 ohms and at 110°C 142.29 ohms.
…
[/code][/quote]
Would a PT1000 be a better sensor for the VM110? If so, what would be the most suitable resistor value to use in series with the PT1000?
Thanks
Simon Morgan
I think there is no big advantage to use PT1000. Anyhow the voltage span is very low.
Do you have any specifications for the sensor Pt1000 you are going to use? There you may check the recommended current for it. The problem is the self heating of the sensor element.
Anyone can help me out here please…
I would like to use the K8055 for temperature control from the swimmingpool pump. Problem is that when I connect a PT100 sensor to it the accuracy is not enough…as I’m interested only in a temp.range from 10 to 35 degrees.
Any suggestions in what to use and how to connect it???
I alo have a K8067…but the LM335 is unusable as it’s not waterproof…
Thx & regards,
Rob
Doesn’t really answer your query but I have now started using Dallas 1-wire chips for temperature measurement and subsequent control. In UK you can see the spec at homechip.com
They are very easy to use in fact far easier than the PT-1000 type and much cheaper. Quite good fun to experiment with. I guess you could make waterproof by casting the connecting wires in resin.
Of course, if all you are really interested in doing is to control a pump based on water temperature then a simple thermostat similar to a cylinder stat would do the trick for minimal cost.
Simon Morgan
Simon,
I’ll take a look…
But using only a thermostat is not good enough as I want to adjust the filtering frequency according to the water temperature.
Thx for your reply
Rob
I only play at electronics but it would seem (in theory!) to be relatively easy to use a Dallas 1-wire device as sensor and any old laptop as a programmable controller to drive relay(s) to switch on/off a pump. Sounds like a fun project.
I use a very old laptop (Celeron 600MHz) as an instrument recorder for a solar heating system. I admit is doesn’t actually control anything but this shouldn’t prove too difficult.
Look at quasarelectronics.com/3074-8 … -board.htm for simple kit. You could probably also use the Velleman K8055 as the relay controller.
Simon
An even simpler approach could be using this module …
maplin.co.uk/Module.aspx?ModuleNo=31698
Making the sensor waterproof may be a challenge but probably do-able.
Simon
[quote=“robbals”]Simon,
I’ll take a look…
But using only a thermostat is not good enough as I want to adjust the filtering frequency according to the water temperature.
Thx for your reply
Rob[/quote]
As a matter of interest, could you be a bit more specific about “…filtering frequency…”. Not having a swimming pool, I am not too sure what you mean exactly.
Cheers
Simon
Simon,
I took a look at the relay controller -> I use the K8055 at the moment…have about the same functions…
Then the module from Maplin -> is a thermostat => not what I need.
Explanation filtring frequency -> so I need to constantly measure the temperature from the poolwater. The frequency (= hours the pump is on) is changing as the watertemperature is higher. (example: at 5degrees, the pump is on for about 5 hours/day but at 24 degrees the pump has to be on for 17 hours/day)
The problem is that I need a sensor that gives the best readout in a temp.range from 0-40 degrees…and that I can easely connect to my K8055. (if its not waterproof…I’ll make it waterproof…or at least I’ll die trying 
)
Thanks for the support!
Rob
Maybe you can use your K8055 board with something like the LM35 temperature sensor IC.
See national.com/ds/LM/LM35.pdf for data sheet
I would have thought a fairly simple programme on a PC/laptop could then read the temperature and then activate a relay for a certain time. Interesting project!
AS they say on the TV adverts, the possibilities are endless.
Simon