1. Main control circuit 2. Sampling circuit The ICL7650 is a fourth-generation op amp with very low input offset voltage (±1 μV) and offset drift (0.05 μV/°C). Very high open-loop gain (≥120 dB) and extremely low time drift (o.01 μV/h); moderate price; linear output range from 0 to 4.5 V when powered from ±5V; when input voltage is o When the measured gain is 27, the output zero voltage
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The hardware structure of the main control circuit is shown in the figure below. In the figure, the 8031 ​​MCU is the core. The monitoring program is solidified in 4 KB of EPROM2732, 2 KB of RAM6116 is used to store test data, the extended programmable parallel interface 8155 is used as the LED display glyph, and the B port is used as the CMC-50P-2 printer control port. The C port is used as a keyboard control and LED display word position. The 8-bit A/D converter chip selects ADC0809. The P31 port of the 8031 ​​is used as the gain control and shift control of the programmable amplifier. The output of the 74LS273 is latched, and the relay array is controlled by the 7406 driver. 
The principle of the detection bridge circuit is shown in the figure below. The circuit measures the insulation resistance of 20 kΩ--1275 MQ in two steps. The high-end output UXH measures 5 MΩ to 1275 MΩ resistance; the low-range output UxL measures 20 kΩ to 5 MΩ resistance. The P1.3 line of the MCU is controlled by the 7406 driver control relay. 
In order to make 20 kΩ～1275 MΩ, the detection accuracy in the range is not less than 2.5%, the circuit parameters are selected and adjusted according to the following requirements: the resistors constituting the bridge should be selected with a metal film resistor with an accuracy of not less than 1%; the adjustment potentiometer Wl , the total resistance of the B to ground branch is 0.5 (1 ± 0.2%) MΩ; adjust W3, so that the total resistance of the A to ground branch is 5 (1 ± 0.2%) MΩ; Wt is the high resistance measurement bridge balance adjustment Potentiometer; Wz is a low resistance measurement bridge balance adjustment potentiometer.
Bridge balance adjustment method: short-circuit Rx, respectively turn on high-resistance measurement file and low-resistance measurement file, adjust W2 and W4, so that the voltage between Ux and U2 is not higher than 0.5 mV (using 4-digit half-millimeter millivoltmeter) measuring).
3. Programmable amplifier
In order to improve the measurement accuracy, widen the measurement range and realize the automatic switching of the range, the programmable amplifier is used to properly amplify the Ux. In the measurement range of the measured insulation resistance from 20 kΩ to 1275 MΩ, the output voltage Ux is reduced from 4V to 15.625 mV, a change of 256 times. It is not difficult to choose a finished program-controlled amplifier to achieve this function, but it is more expensive. The inexpensive program-controlled amplifier designed by this system solves the problem better. The figure below is the schematic of the circuit.
The circuit consists of an auto-zero chopper amplifier chip ICL7650, an analog switch CD4051 and a resistor network. 2%。 The accuracy of each resistor is selected to be ± 0.2%. The analog switch is designed as follows. Although the on-resistance of the analog switch is large (500 Q), the input impedance is very small due to the high input impedance of the op amp, so the effect on the gain of the amplifier is negligible. The control signals for the analog switches are from P1.0, P1.1, and P1.2. When the control signal changes from (0, 0, 0) to (1, 1, 1), the gain of the amplifier changes from 20 to 27, a total of 8 files, so that the input voltage of the A/D converter is in the range of 2 to 4 V. Internal (the measured resistance is in the range of 20 kΩ to 1275 MΩ). 
Since BTC can easily be exchanged for cash, mining ZEC can be a good way to indirectly fill your bank account or earn cash. ZEC can also be sold directly on some major exchanges.
Mining can be a cheap entry ticket to the Zcash markets, which are loved by traders for their high volatility. If you`re a good and/or lucky trader, you can maximize your profits.</li>
Ever since ZEC hit the market, it`s been one of the highest-priced altcoins on the market, peaking at over $400 in June 2017.
Mining can be a great way to subsidize the purchase of a new high-end GPU (or two, or three-).
Finally, building a large ZEC position through mining now may allow you to take advantage of price appreciation in the future with less risk than you`d face by just buying ZEC.
Let`s break this last idea down a bit further.
Mining and holding crypto is similar to the old adage of buying low and selling high. However most buyers don`t know how to do technical analysis, so they buy and sell at the wrong times.
They buy high during parabolic price increases and sell low during what could be normal price corrections on continued upward trends
Buying gear and mining cryptocurrency with it allows you to own an income-producing asset in the gear itself, with aftermarket resale value holding up very well.
Allowing your gear to earn money and selling that gear when you reach your target can allow you to make nearly all your money back on the gear and pocket the crypto generated as profit.