Testing WVO and biodiesel for water.

[dgs]

I have ordered the capacitive rh sensors from China at £2.07 each. When I contacted the UK company they told me because it was a small order then 1 would cost £32.50- ridiculous!

I will try Maplins first for the meter.

[Julian]

I bet the Chinese price included post too!

Been having a trawl of the web and found this from the Switzerland ...

http://www.ist-usadivision.com/objects/media/data-sheets/product/humidity/MK33-W.pdf

Little info on the company website other than that pdf, but the implication is that is't suitable for use in oil!

Any further info on why it need to be a capacitive sensor?

[dgs]

Yes, You are correct, it does include the postage.

Somewhere in the thread on infopop that Sun Wizard started it did state that the ones that are the resistance type don't work.

I'm not expecting this set up to be ultra accurate like S/B or KF but +/- 50ppm would be more than good enough for a cheap set-up and quick check.  As I've said before the main advantage would be the convenience. Just make sure the sample is at 20 degs, immerse the sensor, wait 2 mins then take the reading and refer to the graph. (well, thats the theory) we will see.

[Manfred]

Hi chaps. I've been reading this thread with interest and went looking today and fount this humidity controller. It's only good for 80c but maybe swap with a better quality sensor and you have an automated controll good for 10KW. So would power your pump and heater. It will humidify or de humidify depending on parameters set. What do you think.


 http://www.ebay.co.uk/itm/220V-Digital-Capacitive-Air-Humidity-Control-Controller-1-99-RH-Sensor-/251892228559?pt=LH_DefaultDomain_3&hash=item3aa5f261cf

[Julian]

Dave,

I'm a skeptical bugger at the best of times.  If someone says something doesn't work I always ask why.  For instance he may  had a capacitive sensor working and tried to replace it, but a replacement, restive sensor may not have worked with his meter.

I've been looking closer at the Arduino humidity monitoring set up.  As I have a both a Uno and a Mega spare along with an LCD display, I'll have a play using a DHT22 sensor (assuming the nice people in China accept my derisory best offer).  Even if I pay full price they are still throw-away money.

Using the Arduino library, the LCD will show both temperature and % humidity.  Assuming it works, if a relationship can be established between the % relative humidity and ppm in oil/bio, it would be quite easy for some smarter than me to write a conversion to display ppm.

Manfred, the sensor on that Willhi unit looks quite like the one that is used in Arduino projects.  Those are also a max of 80°C, but fine for playing with to prove the idea.

[Julian]

You mention sun wizard on info pop, but I found him in this thread ... http://www.burnveg.com/forum/capacitive-wvo-water-measurement-t832.html  on a forum with the rather snappy name of "Vegetable Oil SVO WVO waste cooking oil as biofuel" which he appears to run.

I've never come across this site before, but then I don't do much research on straight veg ... some quite good reading on there though.

[dgs]

Hi Manfred,
I assume you are suggesting the de-humidifier to help dry the biodiesel/oil. Of course this pre-supposes it still has to be heated and bubbled/sprayed, then the moisture in the headspace removed with the de/hum.

I know at one time IMB and the Irish guys experimented with de humidifiers and they did work, the problem was the electric cost for the de/hum. I'm also sure with a bit of experimentation you could get some correlation between ppm water and r/h in the headspace.

Julian, that is a good link and probably explains why Sun Wizard didn't answer my posts on infopop. Please let us know how your tests go. I'm stuck at the moment until I get the sensors and meter from China

[Julian]

The sensors I'm looking at are coming from China too.  Even if they agree the price, it'll take a month or so to get here.

[Bill]

I've now got a Honeywell capacitive sensor as described previously. I'll wire up the power supply over the weekend. Next batch of bio I am going to draw off 5 lts of dried. To start with I'm just going to put the sensor in the bio, stabilise, measure volts, out, rest several minutes and back into the bio. Repeat many times to see if its repeatable or if the sensor dies.
Then split the bio and make some 1 lt of bio samples with a know amount (ppm by weight) of added water. Maybe 200, 500, 800 ppm. Then see if there is a detectable difference between samples.
Make sense? Comments?

[dgs]

That makes sense Bill. How are you going to know your bio is dry before seeding it with water, drying at @ 120degs?

If you need confirmation of any water levels, just send me the samples and I will test with the S/B or KF (when I get some new reagents for it)

[dgs]

That makes sense Bill. How are you going to know your bio is dry before seeding it with water, drying at @ 120degs?

If you need confirmation of any water levels, just send me the samples and I will test with the S/B or KF (when I get some new reagents for it)

When you say you have now got a honeywell sensor, do you mean you have recently got it.

[Bill]

I got a sensor as I described in reply#5 of this topic.
The bio is splash dried (like spray drying but not quite a spray) at 65 C. Not entirely sure of what the base line water content will be but it will be the same for all three trial samples and the unused reference. If it all works that should give me enough information to determine a calibration graph and work out the base line water content of the starting bio. I don't need to know the how much water is in the bio to start with to any great accuracy.
It should also be a method that gives results that can be compared to trials by others.

[Julian]

The offer I placed on a sensor was ignored but I got one on a snipe for a pound including post and another 5 on a snipe for £3.45 including post.  The 1 pound one is supposed to be a more accurate sensor, so I'll wait for the cheap ones to arrive before dunking any in oil.

In the meantime I got the expensive one running with an Arduino Uno.  It seems very responsive ... putting a hot cup of tea down 3 inched from the sensor saw the temperature rise by a few points of a degree and gently blowing from a foot away will noticeably increase the humidity.

In the photos below the white grid thing at the back of the bread board is the sensor, and the screen grab shows the serial print out on the computer.






The window to the left of the results is the Arduino "sketch" as they call it.  It should be fairly easy to get the results displayed on an LCD and to perform "sums" on them to arrive at adjusted values.


There will be many different sketches to use with these sensors, but this is the one I used (it works in conjunction with a library, so much of the code will be elsewhere).  I had a little play to comment out °F and heat index ...

// Example testing sketch for various DHT humidity/temperature sensors
// Written by ladyada, public domain

#include "DHT.h"

#define DHTPIN 2     // what pin we're connected to

// Uncomment whatever type you're using!
//#define DHTTYPE DHT11   // DHT 11
#define DHTTYPE DHT22   // DHT 22  (AM2302)
//#define DHTTYPE DHT21   // DHT 21 (AM2301)

// Connect pin 1 (on the left) of the sensor to +5V
// NOTE: If using a board with 3.3V logic like an Arduino Due connect pin 1
// to 3.3V instead of 5V!
// Connect pin 2 of the sensor to whatever your DHTPIN is
// Connect pin 4 (on the right) of the sensor to GROUND
// Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor

// Initialize DHT sensor for normal 16mhz Arduino
DHT dht(DHTPIN, DHTTYPE);
// NOTE: For working with a faster chip, like an Arduino Due or Teensy, you
// might need to increase the threshold for cycle counts considered a 1 or 0.
// You can do this by passing a 3rd parameter for this threshold.  It's a bit
// of fiddling to find the right value, but in general the faster the CPU the
// higher the value.  The default for a 16mhz AVR is a value of 6.  For an
// Arduino Due that runs at 84mhz a value of 30 works.
// Example to initialize DHT sensor for Arduino Due:
//DHT dht(DHTPIN, DHTTYPE, 30);

void setup() {
  Serial.begin(9600);
  Serial.println("DHTxx test!");
 
  dht.begin();
}

void loop() {
  // Wait a few seconds between measurements.
  delay(2000);

  // Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  float h = dht.readHumidity();
  // Read temperature as Celsius
  float t = dht.readTemperature();
  // Read temperature as Fahrenheit
  float f = dht.readTemperature(true);
 
  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  // Compute heat index
  // Must send in temp in Fahrenheit!
  float hi = dht.computeHeatIndex(f, h);

  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: ");
  Serial.print(t);
  Serial.println(" *C ");
  //Serial.print(f);
  //Serial.print(" *F\t");
  //Serial.print("Heat index: ");
  //Serial.print(hi);
  //Serial.println(" *F");
}

[Julian]

Hmm, really quite impressed with this little thing!

Blowing gently at the sensor from 3 feet away shows a reading change of around 1%.

Even if these things don't work in oil or bio, I think I'll try and rig up a system to run the shower fan.

[Bill]

The sensor I have has not died after repeated and lengthy immersion in dried bio and bio with added water. The readings from bio with added water show an increase in value as water content increases, a hopeful sign. The problem is the increase between samples is small and has a lot of variation. The range of values measured in one sample overlap slightly with the range of values from the sample with the next highest water content. The samples I made up were bio+200ppm, bio+500ppm, bio+800ppm. Maybe this type of sensor is not sufficiently accurate for this type of measurement.
More results at a later date when I've done some statistics.