temp measurement with TC
Hello,
I'm trying to measure the temperature of water flow (5-40 deg C)
through a 1/2" pipe using the BS2. I have little experience with the
stamp, nor with temp measurements.
My best idea is to use a type T thermocouple probe in a 1/16"
compression fitting. Then I would use an IC temp sensor (maybe LM35)
to measure the temp of an a isothermal block. Voltage outputs of the
IC sensor could be digitized by an ADC (Maybe one that's MUX capable
from Analog Devices - or could use multiple LTC1298's). Then, I will
tackle the software issues to compute the temp of the thermocouple.
Is there a cheaper way to do this? Do I need to amplify the signal
from the thermocouple before trying to measure with ADC? Does my
choice of components look reasonable?
Thanks for any feedback,
Eric
I'm trying to measure the temperature of water flow (5-40 deg C)
through a 1/2" pipe using the BS2. I have little experience with the
stamp, nor with temp measurements.
My best idea is to use a type T thermocouple probe in a 1/16"
compression fitting. Then I would use an IC temp sensor (maybe LM35)
to measure the temp of an a isothermal block. Voltage outputs of the
IC sensor could be digitized by an ADC (Maybe one that's MUX capable
from Analog Devices - or could use multiple LTC1298's). Then, I will
tackle the software issues to compute the temp of the thermocouple.
Is there a cheaper way to do this? Do I need to amplify the signal
from the thermocouple before trying to measure with ADC? Does my
choice of components look reasonable?
Thanks for any feedback,
Eric
Comments
I did a similar thing for a hot tub. I did not use a thermocouple
because of its very small output. Instead I constructed a probe using
an LM34 (°F) (you can use a LM35 for °C) along the lines the probe
described in http://www.dalsemi.com/news/resource/rsc5_1820.html. I
brought the 3 wires out thru a well shielded cable and ran it 20 feet
or so to the BS2. I got my stainless steel probe from Omega as
suggested. I grounded the probe but did not ground the sensor to the
probed.
For an ADC I selected the Maxim MAX187 for its simple, time
independent, interface and for its 1 count per millivolt of input.
A snippet of my code is:
' Maxim MAX187 Analog/Digital Converter (conversion time <8.5us)
' 12 bits, full scale is 4.096 volts
' ADC reads in millivolts = decidegrees
adcclk con 13 ' Output pin for ADC clock line
adccs con 14 ' Output pin for ADC chip select
adcdl con 15 ' Input pin for ADC serial data line
adcctr var byte ' counter for ADC clocks
low adccs ' enable adc chip select
tempmeas = 0 ' init result
for adcctr = 1 to 12 ' data read time about 20ms total
tempmeas = tempmeas << 1 ' shift left
pulsout adcclk,1 ' 2 us clock pulse
tempmeas = tempmeas | ins.lowbit(adcdl)
next
pulsout adcclk,1 ' thirteenth clock
high adccs ' disable chip select
' we're done with adc
This will give you a resolution of 1/10 degree.
Finally, to display the temperature I used the LED AppMod from
Parallax. The code for it is a little tougher.
I hope this helps.
--- In basicstamps@y..., capnmeier@y... wrote:
> Hello,
> I'm trying to measure the temperature of water flow (5-40 deg C)
> through a 1/2" pipe using the BS2. I have little experience with
the
> stamp, nor with temp measurements.
> My best idea is to use a type T thermocouple probe in a 1/16"
> compression fitting. Then I would use an IC temp sensor (maybe
LM35)
> to measure the temp of an a isothermal block. Voltage outputs of
the
> IC sensor could be digitized by an ADC (Maybe one that's MUX capable
> from Analog Devices - or could use multiple LTC1298's). Then, I
will
> tackle the software issues to compute the temp of the thermocouple.
> Is there a cheaper way to do this? Do I need to amplify the
signal
> from the thermocouple before trying to measure with ADC? Does my
> choice of components look reasonable?
> Thanks for any feedback,
> Eric
described was a probe made from an Omega SS-14 or similar. Attach
wires to the sensor. Put heat sink compound in the end of the probe (I
used a straw and puffed it in place). Slide the sensor into the tube
and seal the open end of the tube with a moisture resistant epoxy...
Sorry, I should have tested the link before I quoted it.
--- In basicstamps@y..., fdavidson@m... wrote:
> Hi Eric,
>
> I did a similar thing for a hot tub. I did not use a thermocouple
> because of its very small output. Instead I constructed a probe
using
> an LM34 (°F) (you can use a LM35 for °C) along the lines the probe
> described in http://www.dalsemi.com/news/resource/rsc5_1820.html. I
> brought the 3 wires out thru a well shielded cable and ran it 20
feet
> or so to the BS2. I got my stainless steel probe from Omega as
> suggested. I grounded the probe but did not ground the sensor to the
> probed.
>
> For an ADC I selected the Maxim MAX187 for its simple, time
> independent, interface and for its 1 count per millivolt of input.
> A snippet of my code is:
>
> ' Maxim MAX187 Analog/Digital Converter (conversion time <8.5us)
> ' 12 bits, full scale is 4.096 volts
> ' ADC reads in millivolts = decidegrees
> adcclk con 13 ' Output pin for ADC clock line
> adccs con 14 ' Output pin for ADC chip select
> adcdl con 15 ' Input pin for ADC serial data line
> adcctr var byte ' counter for ADC clocks
>
> low adccs ' enable adc chip select
> tempmeas = 0 ' init result
> for adcctr = 1 to 12 ' data read time about 20ms total
> tempmeas = tempmeas << 1 ' shift left
> pulsout adcclk,1 ' 2 us clock pulse
> tempmeas = tempmeas | ins.lowbit(adcdl)
> next
> pulsout adcclk,1 ' thirteenth clock
> high adccs ' disable chip select
> ' we're done with adc
>
> This will give you a resolution of 1/10 degree.
>
> Finally, to display the temperature I used the LED AppMod from
> Parallax. The code for it is a little tougher.
>
> I hope this helps.
>
> --- In basicstamps@y..., capnmeier@y... wrote:
> > Hello,
> > I'm trying to measure the temperature of water flow (5-40 deg C)
> > through a 1/2" pipe using the BS2. I have little experience with
> the
> > stamp, nor with temp measurements.
> > My best idea is to use a type T thermocouple probe in a 1/16"
> > compression fitting. Then I would use an IC temp sensor (maybe
> LM35)
> > to measure the temp of an a isothermal block. Voltage outputs of
> the
> > IC sensor could be digitized by an ADC (Maybe one that's MUX
capable
> > from Analog Devices - or could use multiple LTC1298's). Then, I
> will
> > tackle the software issues to compute the temp of the
thermocouple.
> > Is there a cheaper way to do this? Do I need to amplify the
> signal
> > from the thermocouple before trying to measure with ADC? Does my
> > choice of components look reasonable?
> > Thanks for any feedback,
> > Eric