Ohmmeter – Simple Resistance Measurement

 Discrete-Circuits, Test-Measurement  No Responses »
Feb 172009
 
Ohmmeter - Simple Resistance Measurement

Measurement of resistor values in circuit configurations are required to be made often, as these might have changed in value due to various tolerance ranges, and hence could be the cause of faults. Likewise the resistance of components used in a circuit, may need to be known. In such cases the measurement of resistance is a must. The circuit used for measurement of voltage can be modified to measure the value of the unknown resistance. The principle followed is the measurement of voltage drop across the resistance when a constant current flows through it. In the voltage measuring circuit, the Read More …

 Posted by at 5:10 AM

Ammeter and Precision Rectifier

 Opamp-Circuits, Test-Measurement  No Responses »
Feb 162009
 
Ammeter and Precision Rectifier

Studying current measurement is a prerequisite for many of the measuring techniques. The current parameter mainly specifies the power consumption in a circuit, given the value of resistance. It is found convenient to measure current rather than voltage for knowing power output and determining efficiency. It may be required to measure leakages in circuits at certain times. Hence the measurement of current constitutes a priority. Measurement of DC Current – The circuit diagram for the measurement of current (d.c. and a.c. modes) is shown aside. For measurement of current switch SI is operated. The switch S-ad is kept in d.c. Read More …

 Posted by at 2:32 AM

Voltage to Current Source 4-20 mA

 Opamp-Circuits  No Responses »
Feb 162009
 
Voltage to Current Source 4-20 mA

The 0-1V to 4-20 mA Converter published earlier is a current sink, Here is a circuit that is a voltage to current converter but with a current source. You can use a LM358 or LM324. The first opamp is a Voltage to Current with a sink output. That current creates a varying voltage w.r.t the 12V DC supply, this varying voltage is mirrored by the second opamp across the source output resistor. This way a constant current is obtained with a sourcing output. The control elements are small signal high gain transistors. Any suitable equivalent can be used. Even the Read More …

 Posted by at 12:50 AM  Tagged with:

Three Point Preset Counter

 Timers-Counters  No Responses »
Feb 122009
 
Three Point Preset Counter

This is a prototype of a Preset Counter. It is built with ICM7217. The cabinet is ABS Plastic DIN 96-96. The Panel is Engraved on Acrylic. I don’t remember for which application it was used. It has three thumbwheel settings, when the proximity switch counts upto the set-value, the corresponding relay turns ON, with a State Indicating LED on front panel. These can be configured sequentially or to work synchronously, this depends on what customer wants. Both modes may give the same result. In sequential operation, Some of these counters-timers may need to wait for an external trigger or feedback Read More …

 Posted by at 1:00 PM

Proportional Temperature Controller

 Process-Controllers  No Responses »
Feb 112009
 
Proportional Temperature Controller

Proportional Temperature Controller This is a Proportional Controller where the setpoint is derived from a Thumbwheel switch. The conversion of Thumb-wheel Digital Data to Analog mV is similar to R-2R Weighted Resistor Network. In this case it is a 1-2-4-8 Binary Weighted Resistor Network. It has no Digital Components. You can see an example circuit below for digit weights you just use like 10K-100K-1M etc. There is a problem of procuring 8M Resistors, so use series parallel combinations, avoid open presets. Trimpots can be used but then it raises the BOM cost. 1-2-4-8 Kilo Ohms may load opamp for high Read More …

 Posted by at 3:00 PM

Proportional Process Controller

 Process-Controllers  No Responses »
Feb 112009
 
Proportional Process Controller

Proportional Process Controller Specifications Front Panel Controls Display – Process Value PV This is a 3 1/2 digit display which shows the process value from 000 to 1999 as chosen by user it could be deg C, Kg/cm2 or Lts/hr. Push Switch – Displays Setpoint This is a push switch which when pressed, makes Display read SetPoint as required by user to control his process. On-Output Status LED Indicates Relay ON or OFF in Relay and Pulse Output Units. Units with 0-10V or 4-20mA, Output LED is always OFF. Vary SetPoint SP This is an endless 10 Turn Potentiometer this Read More …

 Posted by at 10:16 AM
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