Resistance Measurement Analog LED Meter

 LED-Circuits, Opamp-Circuits, Test-Measurement  No Responses »
Feb 212009
 

This is a LED Analog Meter, This can be used as a Resistance Meter and Low Impedance Voltmeter for Battery Levels. To measure battery voltage, the R5-R12-R17 etc. part of the Reference Resistor Divider Network can be modified to suit. Shown here is for 4 LEDs, Use Three LM324 for 12 or More LEDs and Cascade as shown.

Resistance Measurement Analog LED Meter

This cannot Measure Voltage levels from High Impedance Sources, will work for Battery Voltage Tests. To make it into a Continuity tester. R27 must be a short and R23 5 Ohms. The Black probe should have a Built in Resistance of 2 Ohms. If you want it to be a dedicated voltmeter, remove R3, The Probe has to be a 10X Attenuator with 10M Ohm and The Resistor Divider Steps in 100mV per Step. The R27, R23 etc. is 20K. A Leakage Tester a Mains Voltage Monitor are other possibilities. Use LM3914 for a easier solution. A nice book for your Design Library – Measuring Circuits By Rudolf F. Graf

 Posted by admin at 8:35 PM

Analog Level by BCD Thumbwheel Switch

 Opamp-Circuits  No Responses »
Feb 202009
 
Analog Level by BCD Thumbwheel Switch

BCD Thumbwheel Switch is used to input-set data in digital form, this can be read by digital circuits, uC and uP systems and PLC-SCADA Interfaces. In the early transition of analog to digital, before uP became acceptable, Digital systems without uP were made, it even had printers, RAM and displays. The uP systems were coming in, uC had not yet come and uP systems had to still win the confidence of the Prudent Industrial Design Engineer. The drawbacks of uP based systems used in Computers, in those days were. Power Consumption was very high, needed SMPS. Many chips, a CPU Read More …

 Posted by admin at 1:05 AM

Opamp Supply on Buffered Virtual Ground

 Opamp-Circuits, Power-Supplies  No Responses »
Feb 192009
 
Opamp Supply on Buffered Virtual Ground

When a Inverting Opamp Configuration is at a steady state, we say the Inverting Input is at a Virtual Ground. That means it is at 0V w.r.t to the dual power supply ground, but it cannot drive or draw any current. It is at a high impedance, but still at 0V. When you buffer this 0 V, you get a low signal ground for a opamp supply. This gnd. can sink and source in a couple of mA. You can use it with low power opamp circuits for portable battery operated devices. This creates a virtual +/- 6 V dual Read More …

 Posted by admin at 5:31 AM

Voltage to Frequency Converter ICL8038

 Mixed-Circuits  No Responses »
Feb 192009
 
Voltage to Frequency Converter ICL8038

This was a small circuit made for driving an Impact counter. The heart being ICL8038. It must have been a Motor driving a Conveyor, the motor has a feedback attachment called Tachogenerator. Only part of the circuit is shown here. See the image of product here Tacho Counter. The configuration is derived from the Application Notes of Intersil. The Voltage from Tachogenerator is Measured on a DPM-DVM and also fed to this circuit after attenuation and filtering. The square pulses of 8038 is used to derive a Logic pulse train for a CD4040. The CD4040 works of 0 and 12V. Read More …

 Posted by admin at 2:40 AM  Tagged with:

Millivolt Source – Field Calibration Current Loop

 Opamp-Circuits, Test-Measurement  No Responses »
Feb 192009
 
Millivolt Source - Field Calibration Current Loop

This is easy to rig millivolt source for field calibration or troubleshooting of 4-20 mA current loops. Here a Darlington pair is used for current amplification which reduces the Ib error as gain is very high. A rotary switch selects, 4-12-20 mA Preset points. A Bourns multi-turn wirewound Pot can also be used with a digital dial. Enclose in a dust proof handheld box. Read more on process calibration.

 Posted by admin at 1:20 AM  Tagged with:

Precision Op-Amp Current Source

 Opamp-Circuits  No Responses »
Feb 182009
 
Precision Op-Amp Current Source

In this circuit we tackle the error indicated in the earlier Current Source. The LM336-2.5V eliminates the tiny error of the regulated supply and resistors. Thereby increasing Precision to a higher degree. The opamp mirrors the stable 2.5V across P3 + R13. With P3 Bourns 10 Turn Trimpot you can trim the current for calibration. Q1 BC557B having a Beta – hfe of 200 is used. But a higher gain or a FET here may reduce error further, that may be needed if you are going for 16 Bit or more resolution. Then even opamp needs to change. Suppose you Read More …

 Posted by admin at 10:31 PM  Tagged with:

Current Source for Resistance Measurement

 Opamp-Circuits, Test-Measurement  No Responses »
Feb 182009
 
Current Source for Resistance Measurement

Here is a current source you can build for resistance measurement. When the current is held constant, you know as per Ohm’s Law the Voltage across Resistor is proportional to Resistance value. The supply is +12 and -12, The total voltage across R6 + R7 is 24V. Then 24V / 120K = 0.2mA. The voltage across R6 is (10K * 0.2mA) = 2V. The same is reflected across R5 in this feedback configuration. That means Q3 is a 2V / 1K = 2mA source. If my calculations are right. There are sources of errors in this circuit. The temperature variation Read More …

 Posted by admin at 8:31 AM
 Older Entries
© 2011 delabs Schematics - Electronic Circuit Suffusion theme by Sayontan Sinha