Microvolt uV signal source

Introduction: Generate stable uV-level voltage signals, used to simulate signals of thermocouples, pressure sensors, etc., to facilitate development, debugging, calibration and troubleshooting occasions

1. Product Introduction: Generate stable uV-level voltage signals, used to simulate various types of thermoelectrics Couple (K, E, etc.), or signals from pressure sensors, etc., to facilitate development,


debugging, calibration and troubleshooting. 2. Application scenarios: Most sensors generate weak voltage signals, which are useful in equipment development, debugging, calibration and troubleshooting. In troubleshooting situations, sometimes it is necessary to make the sensor produce large signal changes, which can be difficult. At this time, it is very convenient to use this signal source to simulate the sensor signal.


3. Product overview:

Battery-powered, no need for boost or negative voltage circuits, no DC/DC noise, and the signal source is clean and stable.
A multi-turn potentiometer adjusts the output amplitude and is a pure analog circuit. As long as the potentiometer is good enough, the resolution is theoretically infinite.
Because I didn’t have a tabletop, I used a Fluke thermometer to measure indirectly. The K-type thermocouple can be stable at 0.1°C, and based on this, the conversion stability is not less than 4uV. Friends who have the conditions can use precision instruments to measure and share the results.
The output range can be adjusted in a small range through the potentiometer. If the requirements are not met, the peripheral resistance of the op amp can be changed to adjust.
It is powered by two AA batteries by default. It can also be powered by lithium batteries as shown in the picture, but additional charge and discharge protection needs to be implemented.
A potentiometer adjustment interface is reserved, which can be connected to a high-precision DAC circuit to achieve digital adjustment.


4. Product parameters:

Default output range: -13mV - 64mV
Resolution: no less than 4uV
Noise level: better than 4uV
Power supply range: 2.5V - 5V
PCB size: 80mm * 50mm


5. Instructions/tutorials:

front and back of the product See the reference design download section.


Instructions for use:

Insert the battery and turn on the switch. Connect the mV scale of the multimeter to the output interface, adjust the output voltage amplitude through R4, and adjust the output range through RP1. After adjustment, it can be used normally.


Note:

Short-term short-circuit output has no effect, but long-term short-circuit output is not recommended.


6. Remarks:

This module is pure hardware, ready to use.
It is recommended to use the models provided by the BOM for the op amp and reference chip, which are selected through repeated experiments. Other models of chips with capacitive loads may cause oscillation.
For occasions with low requirements, domestic potentiometers can be used. For high-precision occasions, it is recommended to use imported Burns potentiometers.
The batch cost of using domestically produced potentiometers is estimated to be around 40 yuan, while the imported Burns potentiometers are around 80 yuan. If the battery box and switch are replaced at low cost, the cost can be reduced by about 10 yuan.
If you want to use a lithium battery, any lithium battery will do. I just used the battery I removed from somewhere else.
If you need to change the output range in a large range, it is recommended to simulate first and then do it to improve efficiency. The simulation tool uses LTspice. For relevant simulation files, see the attachment "uV signal source simulation file.zip".