What is the electronic component resistor calculated?

Black 0, Brown 1, Red 2, Orange 3, Yellow 4, Green 5, Blue 6, Violet 7, Gray 8, White 9, The first and second digits of the four-ring resistance are the effective values, the third is the magnification, and the fourth is the error, and the error is basically gold, that is, 5%, for example, the first ring of a resistor is green, the second ring is brown, the third ring is red, and the fourth ring is gold, so the resistance value of this resistance is 51*100=5100 ohms = error 5%.

The resistance of the five rings is the same as the four rings, but the third ring is the effective value, the fourth ring is the magnification, the fifth ring is the error, and the common one is 1% brown. Five-ring resistors are more difficult to identify than four-ring resistors, because it is difficult to tell which resistance value is if both sides are brown.

Define the formula: r= l s

Variation of Ohm's law: r=u i

Resistance series: r=r1+r2+r3+.rn

The meaning of resistor is resistance, not a certain device of resistance.

Formula for resistor calculation:1) r= l s (where the resistivity of the resistor is determined by its own properties, l is the length of the resistor, and s is the cross-sectional area of the resistor).

2) Definition: r=u i.

3) Total resistance in series circuit: r=r1+r2+r3+......rn。

4) Total resistance in parallel circuit: 1 r=1 r1+1 r2+....Prudence....+1/rn。

5) Finding the resistance by electrical power: r=u p; r=p/i²。

Influencing factors1. Length: When the material and cross-sectional area are the same, the longer the length of the conductor, the greater the resistance.

2. Cross-sectional area: When the material and length are the same, the smaller the cross-sectional core product of the conductor, the greater the resistance.

3. Material: When the length and cross-sectional area are the same, the conductor resistance of different materials in the hail bureau is different.

1. This circuit is a typical instrument amplification circuit.

The instrument built by yourself with the op amp is used as a large circuit (as you see above), which has the advantage of flexible circuit and low cost; The disadvantage is that the op amp parameters should be as symmetrical as possible.

There is also an instrumentation amplifier (AD623), which integrates this large circuit into it, and its gain fiber can be adjusted according to a resistor, and the relationship between the specific resistance and gain will be given in the general specifications. The advantages of this circuit: simple circuit design, strong anti-interference ability; Cons:

**Generally more expensive.

2. About the calculation of the above circuit:

3. About the role of R7, R8, RP:

In the instrumentation amplifier circuit, because it is a differential input of the stove vertical, it needs to be zeroed out, that is, a reference voltage needs to be given, and this reference voltage is accumulated into the output as an offset. For example, the AD623 integrated instrumentation amplifier has a discipline REF, and the output can be adjusted by external reference voltage.

The R7, R8, and Rp in the figure above should also have this effect, where Rp should be much smaller than R7, R8 to ensure that the gain of the amplification circuit is not affected much, but the adjustable range is not so wide.

In fact, there is also a way to adjust the zero point, that is, without using R7, R8, RP, directly let R6 ground change to R6 followed by a reference voltage (that is, the zeroing network of the integrated instrumentation amplifier).

4. Having said so much, my mouth is thirsty, hurry up.