J
Jeffrey Drake
- Jan 1, 1970
- 0
I am in the midst of designing an ohm meter. Due to certain design
constraints, I must use a Basic Stamp II for the first design. Later
designs will likely replace it with a real microcontroller.
I have been considering components to satisfy my needs.
I have been considering using an LM334Z (TO-92) to supply a constant
current source. I am thinking about this one, because with a diode and
a resistor it can provide a temperature independent current source,
which I can supply the load resistor that is being tested. This way, I
can get a nice linear relationship that is not possible with a
wheatstone bridge. I have found the LM334Z to be $1.50 on digikey.ca
(note Canadian), but would like a cheaper variety.
To display the results, I have been looking at an LTC-4727JR 4 digit
16 DIP 7 segment display ($2.95 @ 5 quantity) but unsure what kind of
chip I can use to drive it.
I am looking into a digital potentiometer to provide an autoranging
ability.
One of the drawbacks to the Basic Stamp II is that it has no ADC on
it. I have found a project page that mentions the MAX187, but it is
insanely expensive on digikey. I have found other ADCs that are more
reasonably priced, but unsure what to look for.
Any suggestions?
- Jeffrey Drake.
constraints, I must use a Basic Stamp II for the first design. Later
designs will likely replace it with a real microcontroller.
I have been considering components to satisfy my needs.
I have been considering using an LM334Z (TO-92) to supply a constant
current source. I am thinking about this one, because with a diode and
a resistor it can provide a temperature independent current source,
which I can supply the load resistor that is being tested. This way, I
can get a nice linear relationship that is not possible with a
wheatstone bridge. I have found the LM334Z to be $1.50 on digikey.ca
(note Canadian), but would like a cheaper variety.
To display the results, I have been looking at an LTC-4727JR 4 digit
16 DIP 7 segment display ($2.95 @ 5 quantity) but unsure what kind of
chip I can use to drive it.
I am looking into a digital potentiometer to provide an autoranging
ability.
One of the drawbacks to the Basic Stamp II is that it has no ADC on
it. I have found a project page that mentions the MAX187, but it is
insanely expensive on digikey. I have found other ADCs that are more
reasonably priced, but unsure what to look for.
Any suggestions?
- Jeffrey Drake.