1mA precision current source circuit

[andybarrett1]

Hi

Looking for a easy way of getting a 1mA source.... So Ideas welcome...

It is for field calibrations by techs that loose things.... They ARE not loosing another Fluke 715 '

Ideally needs to operate from a single 9v battery, 0.1% accuracy.

Sure it can be done with op-amp but would have thought a single 8pin chip would do it nowadays?

Looking forward to hearing / seeing some ideas

TY
Andy

[Christopher]

[ralphd]

Use a .05% accurate meter to hand-pick a tl431 and 2.5K resistor that are within your .1% accuracy requirement.  With a small piece of protoboard and a 9v battery clip, your total cost is still under 50c.

[andybarrett1]

I saw this but the REF102 Needs at least 11.4V Supply 

I need to use a 9v PP3 

BR Andy

[Christopher]

The 10v ref just makes the calcs easier. A boost converter won't be the most ideal solution because of noise but is certainly possible

How about a 1v reference and a different sized resistor?

[eas]

Use a .05% accurate meter to hand-pick a tl431 and 2.5K resistor that are within your .1% accuracy requirement.  With a small piece of protoboard and a 9v battery clip, your total cost is still under 50c.

If his time is worth nothing, or he's doing it for fun/learning/etc.  Sounds like this is for work though...

Here is an idea. Follow ralphs suggestion, or something like it, but make each tech test and select the parts and assemble the source. Perhaps they'll be less likely to loose it if they put some effort into making it?

[TimFox]

What will you connect the 1 mA source to?  If it is a very low resistance, than a simple voltage regulator plus series resistor suffices (adjusting the resistor as required).  Otherwise, follow the suggestions above for actual constant-current sources.

[dom0]

LT3092?

At 0.1 % accuracy you will need to trim it, but it's reasonably accurate OOB so the trim adjustment doesn't need to cover a lot of range.

[andybarrett1]

Use a .05% accurate meter to hand-pick a tl431 and 2.5K resistor that are within your .1% accuracy requirement.  With a small piece of protoboard and a 9v battery clip, your total cost is still under 50c.

Have today ordered up a few bits along these lines to play with..... If this works will be the way forward.

Thank you for ALL replies

Appreciated
Andy