Electronic Circuit Design

Digital weight Indicator - Strain Gauge

Posted by on Nov 09, 2020 in Weighing-Scales

I need some details of a digital weight Indicator.
mail from CA

Digital Weight Indicators and Weighing Scales use Strain Gauges mounted on a Stressed Beam, Cantilever or Plate which is also Elastic, means springs back to old shape.

Strain Gauges are bonded to these plates and connected in a Wheatstone bridge circuit. The output of these are very low, as less as 5mV. These are amplified close to the sensor and usable outputs in volts, like 0-10V are used to display the parameter or control the systems.

Fluids Weights are measured with pressure sensors also. Which also have a mini strain gauge or piezoelectric sensor to convert weight to millivolts.

delabs

What is Saturation in Transistors

Posted by on Nov 05, 2020 in Learn-Electronics, Transistor

Date 8/30/06 Simon and delabs
Simon: hello,
delabs: hello

Simon: we have many meanings for saturation,
delabs: means turning on, also means no longer linear, or it is got fixed up, not varying in accordance to any formula

Simon: that is what is concluded of. but we just wanted to be sure.
delabs: like you put salt in water. after some time no more salt can be dissolved, that is the state of saturation, In Electrical, no more relationship with V - I - R. Any increase in voltage or reduction it is same

Simon: thanks
delabs: anytime

Bipolar transistors are so named because their operation involves both electrons and holes. These two kinds of charge carriers are characteristic of the two kinds of doped semiconductor material; electrons are majority charge carriers in n-type semiconductors,

This concludes this episode of Saturated Talk with Simple Simon. Next week, a new Episode which will cover effects of Lightning Bolts.

To learn more about Saturation in NPN and PNP Devices see - Transistors Williamson Labs

Transistor Operation - A transistor in a circuit will be in one of three conditions. Cut off (no collector current), useful for switch operation.In the active region (some collector current, more than a few tenths of a volt above the emitter), useful for amplifier applications.

Chapter 5: Bipolar Junction Transistors

"Saturation also implies that a large amount of minority carrier charge is accumulated in the base region. As a transistor is switched from saturation to cut-off, this charge initially remains in the base and a collector current will remain until this charge is removed by recombination."

Lessons In Electric Circuits - Bipolar Transistors

When a transistor has maximum current through it, it is said to be in a state of saturation (fully conducting).

Building a mV Milli-Volt Calibrator Source

Posted by on Nov 01, 2020 in Process-Calibration

Hi, I am trying to build this mV source that you have drawn on your site. It requires a 5vdc power source with a 1k resistor in line with a 10K pot. Your schematic shows also with the pot a 10k resistor and a 100E component which I have no idea what that is.

My question to you is... does the 10K pot include the 10K resistor and the 100E component or are they separate from the pot? If they are separate, what is the 100E component?

Thanks, KN USA

Dear KN

I would like to know the Circuit File you were referring, i have many on my site for instruments. Let us understand the Theory so you can build your own.

First - You need a Regulated Power Supply for these circuits to be accurate enough. We do not need things like 0.01% for Industrial Electronics or Field Calibration. You can always keep one of these accurate ones in your Lab.

Building a mV Milli-Volt Calibrator Source

Second - Now to bring down the Voltage of say 5V to mV, we need to Attenuate right. An attenuator contains Two Resistors. The High Value - like 1K is a Fixed MFR 1% Resistor. This faces the 5V and Then comes a Multiturn Pot, preferably Bourns or Spectrol 10 turn, This is 10K. These two form just the One part of the attenuator.

See another design here Current Source mA for calibration

Third - This is a 50 ohm or 100 ohm shunt made of 1/2W MFR 1% or Resistors in parallel to get the value. The reason being that the shunt should not even warm up. The 1K resistor is to protect the pot when wiper is at the 0 ohms end and the shunt is shorted by some mistake. If all these can be built in a box with a fixed temperature using an artificial oven. AND. If you make the Regulated Supply using Opamps and a Precision Reference. You have Laboratory grade Instrument, almost.

This is the site location that I am referring to. The 100E is confusing me.

Building a mV Milli-Volt Calibrator Source

Thanks

In this Circuit, The 100 ohms is very important as it acts like a Low Impedance Voltage Source. In Fluke Sources 50 Ohms is standard. The Voltage across this resistor is in millivolts due to the attenuation.

10K/100 ohms is 10,000 ohms divided by 100 ohms. That gives a Divide by 100

5 Volts divided in 100 parts Gives 50 mV (approx as we have the bourns 10 turn pot before the 10K/100 ohms divider. )

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.

You can also use one of the Arduino Analog Outputs and Attenuate them after filtering with a cap. This creates a Programmable Millivolt Source.

So, the 100E is just a 100 ohm resistor aside from the 10K pot? What does the "E" stand for?

E means Ohms. Philips used this notation first as the Symbol Ohm was difficult to Print.

100 Ohm Resistor is important, when you connect it to a Device to Calibrate it will not load it. A DMM has a 10 Meg Ohm Measurement Load. The Instrument you calibrate must have around 1 Meg or more. That is why we use FET input Opamps to measure the mV of Thermocouples.

That is where the millivolt source steps in, it is a Thermocouple Simulator.

thank you very much
KN

Up-Down counter-timer

Posted by on Oct 12, 2020 in Digital-Counters

(A question answer thread of delabs.net, nearly a decade old)

Presettable Up-Down counter-timer

I am looking for a schematic for a pre settable Up/Down counter that I can build for my church. It needs to be 5 decades. From 0:00:00 to 9:59:59. I ran across your web pages while searching for such a schematic. Can you help me out?

EE

Presettable Up-Down counter-timer-Answer

It appears from the "9:59:59 " you have mentioned, what you need is a timer.It it a count up and count down timer you need, like a clock ?

Can you explain to me how you plan to use this circuit in the church.Visit the links below and see if that is what you want.

delabs

Presettable Up-Down counter-timer-Reply

Thanks for the links. What I need this count down timer for is to allow speakers at the church to know how much time is remaining of their presentation. All of our speakers are taped for later use or review. The speakers giving the presentation usually go over their time limits for the audio tapes. With this unit I am trying to build time can be entered by preset thumbwheel switches. The counter is then started and times out when the counter reaches 0:00:00.

What makes this count down timer different is there will be two seperate displays. A one inch set of seven segment LED's will be in the main console with the rest of the logic. There will also be a 2.5 inch set of seven segment displays remotely connected (anout 3 feet away). The large displays will be what the speakers will see. The small displays will be in the control booth.

I already have the following items gathered up. I am hoping to use these components if I am able. I have the MC14029, the MC14513, the Allegro UDN2597A (to drive the large LED's), the Dallas Semi DS32KHz time base, the MC14020, the MC14013, the large and small LED displays, and the thumbwheel switches (set to 9:59:59 maximum)

I also have some MC14011, MC14490 (Hex Debounce Switch Controller, MC14049, and the R's and C's necessary to complete the circuit.

Does this explain what I am trying to do? I think the MC14029 counters can be used to do all the counting and store the preset values. All I have to do is add the reset at 6 for the tens of seconds and the tens of minutes. However, I don't know how to connect the logic?

The DS32KHz, MC14020 and MC14013 will generate the 1 Hertz (1PPS) signal. That is about all I currently have. That is why I need some help

EE

Presettable Up-Down counter-timer-Answer

below are two circuits in pdf format see if they are ok see... Digital Circuits-2

Circuit 1 - Digital Timer Clock With Preset using Thumbwheel switch.

Circuit 2 - 1 Hz or 1 pps crystal clock using CD4060 and 32768 Hz Crystal.

They have not been tested much... The 4513 control pins 8-4-5-3 connections verify, as i did not get the datasheet.

the circuits will work as concepts are right, but some tweaks in R C values may be required.
the R C values can only be corrected if you have problem in making it work.

the main problem in the R C values may be related to "the reset at 6 for the tens of seconds and the tens of minutes". tell me what changes you may want. this is a presettable count down timer upto 99.59.59 hours.minutes.seconds

delabs

Temperature Meters with Analog Recorder Output

Posted by on Oct 12, 2020 in Industrial-Designs, Temperature-Control, Thermocouples-RTD

I would like to know if you offer a monitoring solution that will constantly measure ambient (air) temperature (say, 0 to 150°F), and provide a corresponding DC voltage output of either 100 mV, 1 V, 5 V, or 10 V. Do you make a unit that can be configured to do this?

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