two-wire V / I converter
V / I converter is a can use the voltage signal the restraint output current of the circuit. Two-wire V / I converter with ordinary V / I conversion circuit different points in the voltage signal is not directly output current in moderation, but to grasp the current consumption of all circuits. At the same time, also extracted from the current loop stable voltage conditioning circuitry and sensor supply. The drawings are two-wire basis of V / I conversion circuit schematic diagram the OP1, Q1, R1, R2,Grid tie inverter, Rs forming a V / I converter. Parse if point A due to certain causes higher than 0V, the op-amp OP1 outputs elevated elevated Re voltage across, the current through the Re in larger negative feedback process. Proportionate to the overall power consumption becomes large, the current through the sampling resistor Rs becomes large, the voltage at point B becomes lower (negative). The result is A point voltage is pulled down through R2. Conversely, if the point A, due to some causes of lower than 0V, will be negative feedback raise back 0V. In summary, the results of negative feedback operational amplifier OP1 virtual short A point voltage = 0V. The following parse Vo gripping principle assumption of total power conditioning circuit output voltage is Vo, flows through the the R1 current I1 = Vo/R1 op amp input terminal can not receive current I1 of all flow through R2 B point voltage VB VB =-Vo power negative with all they feed circuit between only Rs =-I1 * R2 =-Vo * R2/R1 take R1 = R2, R2 two resistors, thus all of the current flowing through Rs with R2. R2 the upper end of the virtual ground (0V), Rs is the top GND. Therefore R2, Rs voltage across a complete, all that is VB.
Commensurate with current sampling resistor Rs and R2 in parallel as. Thus the total current Is of the circuit = VO / (Rs / / R2) if taken R2 >> Rs, Is = Vo / Rs Thus, in Figure 3, taken Rs = 100 ohms, when the regulating circuit when the output 04 ~ 2V, the total consumption of current 4 ~ 20mA if R2 >> Rs is not satisfied, it does not matter, Rs and R2 in parallel (Rs / / R2) is a fixed value Is Vo is still linear correlation, the error ratio coefficient can dispel calibration. In addition to the circuit accurate, the circuit malformations work is also need to two first power consumption as low as possible, save the current but also supply conditioning circuitry as well as transmitter. Second, request a single-supply op amps can work, that assumes power case, the input may still receive 0V input, and can work properly. LM358/324 is the most common but also the price of the lowest single-supply op amps, power consumption 400uA / per op amp simply can receive. Single-supply operation, the input is from-03V ~ Vcc-15V areas can be deformed. If replaced OP07 Narrow amplifier, but in this circuit, since the input does not allow as low as 0V, helpless work. R5 and U1 constitutes a reference source, 25V stable reference voltage occurs. LM385 micropower basis of low cost, 20uA to work more the most flat curve given in the manual 100uA neighboring, the current so dominated by R5 100uA about. OP2 constitute a same amplifier, the benchmark amplification, power conditioning circuitry and sensors. Regulator sparse wide input voltage, low-power, high cost; benchmark enlarged as regulated power supply is a cheap plan,power inverter. The partial circuit may also be a choice of off-the-shelf integrated circuits. For example XTR115/116/105, etc., accuracy and stability than homemade good, its own power consumption is also lower (a symbol can stay more current conditioning circuit and conditioning departments more easily design).
Capital but more than 10 times higher than the plan
two-wire pressure transmitter design
the pressure on the bridge, load cell output signal renaissance men belong mV level signals. This type of small-signal individual request to its first-stage amplifier with a differential amplifier. Ordinary selection of low offset, low temperature drift of the differential amplifier. In addition, the use of two-wire, low power consumption is required. The AD623 is commonly used in low-power fine differential amplifier, is commonly used in the differential output before amplification. AD623 the imbalance maximum 200uV, and temperature floating 1uV / degree, use of protection in individual pressure transmitter with sufficient accuracy. R0 to 04V superimposed on the the AD623 REF feet (5 feet), swap R0 pressure = 0 case to make the output 4mA, and then swap RG output 2000mA, and calibration. Circuit design required careful and proportionate to the pressure bridge sensors in a kilohms resistance, power consumption normally relatively large.
The appropriate decline pressure bridge encouragement voltage current consumption can be reduced. However, the output amplitude also will land, the need to progress the AD623 gain. Figure 6 shows the sensor to take a constant voltage power supply, the semiconductor pressure sensor of the actual utilization of large local caliber of a constant current power supply is required good temperature characteristics, and be able to use an op amp constant current source is formed and its supply encouraged. http://www.gridtieinverter.de/
V / I converter is a can use the voltage signal the restraint output current of the circuit. Two-wire V / I converter with ordinary V / I conversion circuit different points in the voltage signal is not directly output current in moderation, but to grasp the current consumption of all circuits. At the same time, also extracted from the current loop stable voltage conditioning circuitry and sensor supply. The drawings are two-wire basis of V / I conversion circuit schematic diagram the OP1, Q1, R1, R2,Grid tie inverter, Rs forming a V / I converter. Parse if point A due to certain causes higher than 0V, the op-amp OP1 outputs elevated elevated Re voltage across, the current through the Re in larger negative feedback process. Proportionate to the overall power consumption becomes large, the current through the sampling resistor Rs becomes large, the voltage at point B becomes lower (negative). The result is A point voltage is pulled down through R2. Conversely, if the point A, due to some causes of lower than 0V, will be negative feedback raise back 0V. In summary, the results of negative feedback operational amplifier OP1 virtual short A point voltage = 0V. The following parse Vo gripping principle assumption of total power conditioning circuit output voltage is Vo, flows through the the R1 current I1 = Vo/R1 op amp input terminal can not receive current I1 of all flow through R2 B point voltage VB VB =-Vo power negative with all they feed circuit between only Rs =-I1 * R2 =-Vo * R2/R1 take R1 = R2, R2 two resistors, thus all of the current flowing through Rs with R2. R2 the upper end of the virtual ground (0V), Rs is the top GND. Therefore R2, Rs voltage across a complete, all that is VB.
Commensurate with current sampling resistor Rs and R2 in parallel as. Thus the total current Is of the circuit = VO / (Rs / / R2) if taken R2 >> Rs, Is = Vo / Rs Thus, in Figure 3, taken Rs = 100 ohms, when the regulating circuit when the output 04 ~ 2V, the total consumption of current 4 ~ 20mA if R2 >> Rs is not satisfied, it does not matter, Rs and R2 in parallel (Rs / / R2) is a fixed value Is Vo is still linear correlation, the error ratio coefficient can dispel calibration. In addition to the circuit accurate, the circuit malformations work is also need to two first power consumption as low as possible, save the current but also supply conditioning circuitry as well as transmitter. Second, request a single-supply op amps can work, that assumes power case, the input may still receive 0V input, and can work properly. LM358/324 is the most common but also the price of the lowest single-supply op amps, power consumption 400uA / per op amp simply can receive. Single-supply operation, the input is from-03V ~ Vcc-15V areas can be deformed. If replaced OP07 Narrow amplifier, but in this circuit, since the input does not allow as low as 0V, helpless work. R5 and U1 constitutes a reference source, 25V stable reference voltage occurs. LM385 micropower basis of low cost, 20uA to work more the most flat curve given in the manual 100uA neighboring, the current so dominated by R5 100uA about. OP2 constitute a same amplifier, the benchmark amplification, power conditioning circuitry and sensors. Regulator sparse wide input voltage, low-power, high cost; benchmark enlarged as regulated power supply is a cheap plan,power inverter. The partial circuit may also be a choice of off-the-shelf integrated circuits. For example XTR115/116/105, etc., accuracy and stability than homemade good, its own power consumption is also lower (a symbol can stay more current conditioning circuit and conditioning departments more easily design).
Capital but more than 10 times higher than the plan
two-wire pressure transmitter design
the pressure on the bridge, load cell output signal renaissance men belong mV level signals. This type of small-signal individual request to its first-stage amplifier with a differential amplifier. Ordinary selection of low offset, low temperature drift of the differential amplifier. In addition, the use of two-wire, low power consumption is required. The AD623 is commonly used in low-power fine differential amplifier, is commonly used in the differential output before amplification. AD623 the imbalance maximum 200uV, and temperature floating 1uV / degree, use of protection in individual pressure transmitter with sufficient accuracy. R0 to 04V superimposed on the the AD623 REF feet (5 feet), swap R0 pressure = 0 case to make the output 4mA, and then swap RG output 2000mA, and calibration. Circuit design required careful and proportionate to the pressure bridge sensors in a kilohms resistance, power consumption normally relatively large.
The appropriate decline pressure bridge encouragement voltage current consumption can be reduced. However, the output amplitude also will land, the need to progress the AD623 gain. Figure 6 shows the sensor to take a constant voltage power supply, the semiconductor pressure sensor of the actual utilization of large local caliber of a constant current power supply is required good temperature characteristics, and be able to use an op amp constant current source is formed and its supply encouraged. http://www.gridtieinverter.de/
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