In the basic measuring circuit given for TGS2442, in the datasheet Page 2 here can somebody help me in understanding how I can supply both Vc and Vh through the same input. And how can i use the transistors to control pulse?

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    \$\begingroup\$ Perhaps you should finish writing your question before submitting it. \$\endgroup\$ – Dmitry Grigoryev Jun 1 '16 at 8:55
  • \$\begingroup\$ The diagram means that Vc and Vh are on the same supply rail, Vc for V-collector (of one of the transistors) and Vh for V-heater \$\endgroup\$ – Sam Jun 1 '16 at 9:52

You need to drive the two transistors with separate control signals.

The PDF at this link is somewhat easier to read.

You can zoom in on the timing diagram in that PDF - in the one you linked to the zoom doesn't seem to work and you (or at least I) can't download the PDF.

The heat pulse begins where the measure pulse ends.

I don't see any reasonable way to drive both with a single signal.

You have a period where one is on followed by a period where the other is on followed by a period where neither is on. I don't see getting that out of one signal without having some extra circuitry, so just use two digital outputs from your controller and save yourself some hassle.

The cycle looks like this:

  1. Activate Vc
  2. Wait 2.5 msec
  3. Read output value
  4. Wait 2.5 msec
  5. Turn off Vc
  6. Turn on Vh
  7. Wait 14 ms
  8. Turn off Vh
  9. Wait 981 msec
  10. Repeat from step 1.

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