| Calibrating resistors using AT89C51RD2 | | 01/01/70 00:00 |
| The problem is not manufacturing tolerances... | | 01/01/70 00:00 |
| those low drift 0.01% resistors are too expensive. | | 01/01/70 00:00 |
| Now, that you enter into a discussion... | | 01/01/70 00:00 |
| more details | | 01/01/70 00:00 |
| Drift is well documented | | 01/01/70 00:00 |
| No longer published in todays datasheets... | | 01/01/70 00:00 |
| thanks that was very useful | | 01/01/70 00:00 |
| You can't calibrate without a reference! | | 01/01/70 00:00 |
| I have a Hioki DMM as a reference | | 01/01/70 00:00 |
| But you said auto-calibration | | 01/01/70 00:00 |
| No | | 01/01/70 00:00 |
| Need lots of bits | | 01/01/70 00:00 |
| good analysis | | 01/01/70 00:00 |
| what design? | | 01/01/70 00:00 |
| how precise is that? | | 01/01/70 00:00 |
| 50000 counts | | 01/01/70 00:00 |
| you are making the usual mistake of .... | | 01/01/70 00:00 |
| not just more precise, but lower drift as well | | 01/01/70 00:00 |
| Calibration | | 01/01/70 00:00 |
| can I regularly calibrate? | | 01/01/70 00:00 |
| many issues involved | | 01/01/70 00:00 |
| Then... | | 01/01/70 00:00 |
| Assuming and supposing... | | 01/01/70 00:00 |
| Ok... | | 01/01/70 00:00 |
| How fast? How many bits? How stable input signal? | | 01/01/70 00:00 |
| more details | | 01/01/70 00:00 |
| More details needed... | | 01/01/70 00:00 |
| spikes of source could be a problem | | 01/01/70 00:00 |
| Hhm... | | 01/01/70 00:00 |
| Hard to self-calibrate | | 01/01/70 00:00 |
| high sampling rate is not for calibration | | 01/01/70 00:00 |
| It is a constant current source | | 01/01/70 00:00 |
| Answers and questions... | | 01/01/70 00:00 |
| Answers | | 01/01/70 00:00 |
| Oh, I think I know what it is... | | 01/01/70 00:00 |
| That's true | | 01/01/70 00:00 |
| Difficult! | | 01/01/70 00:00 |
| since this is about calibrating known resistors .... | | 01/01/70 00:00 |
| Too fast for manual change | | 01/01/70 00:00 |
| My solution | | 01/01/70 00:00 |
| I have seen nothing yet that gives .... | | 01/01/70 00:00 |
| How? | | 01/01/70 00:00 |
| two screw terminals and a precision resistor | | 01/01/70 00:00 |
| What are exactly the shunts you switch? | | 01/01/70 00:00 |
| currently ... | | 01/01/70 00:00 |
| You should test... | | 01/01/70 00:00 |
| good idea... | | 01/01/70 00:00 |
| Well, I suspect... | | 01/01/70 00:00 |
| don't expect | | 01/01/70 00:00 |
| A look into datasheet is always important... | | 01/01/70 00:00 |
| Both problems | | 01/01/70 00:00 |
| Advantages of shunts in series | | 01/01/70 00:00 |
| Current scheme... | | 01/01/70 00:00 |
| How make before break? | | 01/01/70 00:00 |
| It is parallel like your second scheme. | | 01/01/70 00:00 |
| Offset voltages? | | 01/01/70 00:00 |
| Yes | | 01/01/70 00:00 |
| Try the following... | | 01/01/70 00:00 |
| Wht's the difference? | | 01/01/70 00:00 |
| You should, to find out what's wrong! | | 01/01/70 00:00 |
| Ok but Isn't it easier to calibrate? | | 01/01/70 00:00 |
| Yes, but... | | 01/01/70 00:00 |
| Purpose of auto calibration | | 01/01/70 00:00 |
| No! | | 01/01/70 00:00 |
| Did you think about the shunt error during the "make"? | | 01/01/70 00:00 |
| disadvantages of series scheme | | 01/01/70 00:00 |
| Not really... | | 01/01/70 00:00 |
| 0.1% | | 01/01/70 00:00 |
| Surprise! | | 01/01/70 00:00 |
| voltage drop | | 01/01/70 00:00 |
So low? | | 01/01/70 00:00 |
| momma! I want it all, but refuse to pay | | 01/01/70 00:00 |
| Wanting to achive a precision of 0.01%... | | 01/01/70 00:00 |
| next he will make a perpetuum mobile | | 01/01/70 00:00 |
| how true and ... | | 01/01/70 00:00 |
| Precise enough | | 01/01/70 00:00 |
| that MAY be true for VOLTS | | 01/01/70 00:00 |
| OK, give me a few days time.... | | 01/01/70 00:00 |
| Try to avoid it at all! | | 01/01/70 00:00 |
| You need a lot of individual precision for 0.1% all-range | | 01/01/70 00:00 |
| Owens | | 01/01/70 00:00 |
| Yes | | 01/01/70 00:00 |
| Good discussion but... | | 01/01/70 00:00 |
| a hypothetical example | | 01/01/70 00:00 |
