[Module] AD637 effective value measurement module

# 1 Introduction to the module
The function of this module is to convert the effective value of the externally input AC signal into a DC signal output, and can calculate the true effective value of various complex waveforms. The measurable effective value of the input signal can be as high as 7V. For a 1Vrms signal, its -3dB bandwidth is 8MHz. In addition, AD637 can reduce the quiescent current from 2.2mA to 350uA through the chip select (CS) pin. Therefore, it has a wide range of applications in data collection and instrumentation.
AD637 effective value detection module physical picture
! [a4c34333cb93fd63a1fe82cf4775564.jpg] # 2 Module usage
## 2.1 Module characteristics
(1) Wide power supply range: 5V~15V: Wide measurement range: 0~7Vrms.
When +5V power supply, enter the effective value Voltage range: 0~1.4Vrms;
when +12V~±15V power supply, input effective voltage range: 0~7Vrms.
(2) Can measure direct current signals (DC) and alternating current signals (AC).
(3) Maximum measurement accuracy: <1%.
(4) Fast response speed, the slowest response speed measured: <200ms.
(5) Maximum 3dB bandwidth: 8MHz.
(6) The output DC voltage ripple is small: less than 2mV
(7) The module input has an operational amplifier buffer, so the module input impedance is high: 1M; the module is output by an operational amplifier buffer, so the module has a strong load capacity: 10022 ~ +∞.
(8) The input and output interface is flexible and uses two interfaces, one is a terminal interface and the other is an SMA interface.
(9) It has a chip select function: power consumption can be reduced by controlling the chip select pin. The default chip select on the board is valid. Reserved (not soldered) pin interface for chip select control: reserved output voltage effective value calibration function: manual adjustment of potentiometer calibration. Since the on-board circuit design ensures measurement accuracy, the potentiometer is not soldered by default.
( 10) Module size: 70mm×40mm.
## 2.2 Module connection
module connection diagram
! [Connection diagram.png]
## 2.3 Module test
Two sets of data are verified here. After testing, the effective value of the signal can be output. The detailed test will be Later update
the first set of tests 1KHz, amplitude 1V
![5918e433c2fea13e12089b016967586.jpg] Test results:
![e95f002a487a99cf7446571198088cc.jpg] The first set of tests 5KHz, amplitude 5V
![e391d854356ac74974be 3a4ef13117f.jpg] Test results:
![879ef40d5d41bbf2eb7f659765db348.jpg ] # 3 Notes

(1) Power supply instructions: Remember not to connect the V power supply reversely: Since the module is a high-precision analog circuit, please be sure to use a linear DC regulated power supply with a small ripple coefficient, and never use a switching power supply (such The ripple of the power supply is too big!).
(2) When measuring high-frequency signals or small signals, it is strongly recommended that customers solder the SMA radio frequency head and use RF wires for testing, otherwise it may affect the test accuracy.
(3) If the user measures. The signal is smaller and has a higher frequency, which can be achieved by changing the resistance of R3 and R5 in the front stage of the module to
change the amplification factor.
(4) When using the signal source as the module input, be sure to pay attention to the normality of the signal source setting value and the actual value. There will be a mV level deviation, so please use a multi-digit multimeter to measure the actual value. Instead of directly comparing the set value with the output effective value, you should compare the actual value with the measured value.
(5) The above test results are different from the test instrument. Relationship, it is normal for the results of different test instruments to deviate

# Update log
2023/7/21 - First upload of the project
2023/7/31 - Add two sets of tests