How should one build a negative voltage to current converter using op amp(s)?
The answer depends on whether you can float one or both ends of the current load.If you can float both ends, hook one end of the load to the op amp output and tie the other end to ground through a 100 ohm resistor. Now you have a place to sense the output current, at a rate of 100 millivolts per milliamp. feed that back to the negative op-amp input through a 100K resistor, then feed the input to that node through a approx 1.6 megohm resistor, and tie the positive input to about -0.4 volts, and I think you have it.If the current output is to be relative to ground, you need to put the current sensing resistor in the output lead and use a fancier kind of sensing and feedback.
What is the voltage to current converter application?
Application of Voltage to Current ConverterZener diode testerLow AC and DC VoltmetersTesting LEDTesting Diodes
What is a voltage to current converter?
Some circuits need current and not voltage to operate. For example, the deflection coil on the neck of a CRT you find in old TVs and also other inductor loads in general. An opamp inverting amplifier is by default a voltage to current converter if you consider its feed back resistor as load. It also acts like a V to I converter when that resistor is replaced by a capacitor, charging it linearly to give a sweep voltage at the o/p of the opamp.
Capacitance to voltage converter ICs?
You might be able to do this using an integrator. You would place the capacitance to be tested in the feedback loop of an op-amp integrator. With a given input current, the output would be proportional to the capacitance. See this link for some ideas down this line: http://www.national.com/rap/Story/0,1562... Here is another potential design: http://nov55.com/cap/cap1.htm For measuring very small capacitance, a bridge circuit is probably the best option: http://ej.iop.org/links/rRO3OrTgr/rsU0sJ... http://en.wikipedia.org/wiki/Capacitance_meter For measuring very small capacitance you will need to be very careful of the parasitic capacitance of the components you use. These will be much larger than the level you looking at, usually on the order of picofarads.
What are the advantages of operational amplifier(op-amp)?
Very High input impedance, very low output impedance, High gain. Used in differnential amplifier configuration for high CMMR.
How do I convert current into voltage?
A current to voltage converter will produce a voltage proportional to the given current. This circuit is required if your measuring instrument is capable only of measuring voltages and you need to measure the current output.If your instrument or data acquisition module (DAQ) has a input impedance that is several orders larger than the converting resistor, a simple resistor circuit can be used to do the conversion. However, if the input impedance of your instrument is low compared to the converting resistor then the following opamp circuit should be used.To analyse the current to voltage converter by inspection,if we apply KCL to the node at V- (the inverting input) and let the input current to the inverting input be I-, thenVout−V−Rf=Ip+I−(1)[math](1)Vout−V−Rf=Ip+I−[/math]since the output is connected to V- through Rf, the opamp is in a negative feedback configuration. ThusV−=V+=0(2)[math](2)V−=V+=0[/math]and assuming that I- is 0 and simplifying,Vout=IpRf(3)[math](3)Vout=IpRf[/math]
How do I design a voltage-to-frequency converter, only using op-amps, comparators and transistors?
Design a constant-current source using the op amp (sorry, I’m not going to do your homework for you by being more specific).Connect a capacitor to the current source to create a ramp generator.Connect a comparator to the ramp to detect when a threshold voltage is reached - the threshold comparison voltage will be the voltage input.Create an R-S flip-flop with two transistors cross-coupled with inputs to the base of each that can over-ride the input from the other transistor. Connect one input (“set”) to the output of the “high” comparator.Connect another section of the comparator to detect when the ramp goes below a voltage that is the lowest input voltage. Connect the other (“reset”) input of the flip-flop to the output of the “low” comparator.Connect a transistor to discharge the capacitor through a resistor when the “set” output of the flip-flop becomes high.The circuit will now operate as an oscillator with the ramp increasing to the input voltage and then discharging to the low level - the flip-flop output will be a pulse at a frequency that varies linearly with the input voltage. The width of the pulse will be determined by the discharge resistor value.If you want a square wave then use the discharge pulse (flip-flop output) to clock a D flip-flop with the inverse output connected to the D input - this will toggle (change state) with each pulse and generate a variable-frequency square wave.Use a section of op amp to buffer the input as a unity-gain stage and thus isolate the input from the comparison circuitry. This is not theoretically required but is a good practice.
How do I measure voltage and current measurement using arduino?
What are the max and min values of voltage and current you expect to measure? And at what frequency?Update: OK, the answer was a maximum of 24 V, 1.5 A. To read an analog voltage and convert to digital, you need an Analog-to-Digital Converter (ADC). Either you use an external one, or you use the ADC inside the Arduino chip. But these ADCs vary among boards: the Arduino UNO (Ard1) has an ADC with 10 bits resolution and a range between 0 and 5 V and a maximum sampling (acquisition) frequency of 10 kHz; the Arduino DUE (Ard2) has a faster ADC (100 kHz), 12 bits, but a range of only 3.3 V (the power supply of the Ard2). The ADC depends on the microcontroller used in the Arduino board; you can consult its data sheet to get more details.So, to read 24 V you have to attenuate that input voltage with a resistive divider, for instance, eventually with a buffer made with an opamp to connect to one of the Arduino analog inputs (the Ard1 has 6 of them, A0,...,A5).The ADCs in the Arduino read voltages. To read the current, you have to use some form of current-to-voltage converter, and that can be a simple small resistor and Ohm Law :-) (if your circuit tolerates the insertion of that additional resistor) or more complicated I-to-V converters using opamps. All depends on your concrete application. So, the Net has many information. Here are pointers to some.Consult How to Measure High DC Voltage with Arduino to know how to calculate your voltage divider, or this discussion on the topic: How to Measure High DC Voltage with Arduino for measuring currents you have nice pages here Measuring Current with the Arduino or in DC shunt | OpenEnergyMonitor You can find much more pages with interesting information by searching.Final note: Arduino's ADCs don't read negative voltages.