I am using an Adafruit LM4040 to get an accurate external voltage reference. It works very well and I would like to incorporate the circuit into a board instead of tring to use the shield in my circuit.
This is the link to the shield:
The voltage goes through the 750ohm resistor, through the lm4040 voltage reference, then through the 1002 resistor. One leg of the 1002 resistor goes to ground and the other goes to the external aref pin of the Arduino. The 750 ohm resistor requires a .1% tolerance resistance and when I use a voltmeter to check the resistance, it reads 708oms which is closer to 1%. I wanted to check the tolerance of the 1002 resistor to see what tolerance it is. It reads around 4.8k ohms which is almost 50%. I'm sorry, I didn't read the output of the LM404, but when I measure a voltage using the LM4040, it is within .02 volts of what using a voltmeter reads, so it works as I hoped it would. My question is shouldn't I be able to read across a resistor in a circuit and get closer to 10K ohms instead of 4,8K ohms? It seems that the resistor is way out of tolerance. Am I doing something wrong by measuring the resistor in the circuit. I have 10K ohm resistors at 1% tolerance and hoped I can use those resistors instead of a low tolerance resistor at 10K. Help please. Thanks.