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Questions tagged [test]

A definitive procedure that produces a test result.

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29
votes
5answers
11k views

Testpoints: Vias versus pads

I was fixing an ultra cheap home router few days ago and noticed that it had vias marked TP_12V, TP_3V3, TP_GND and similar. The problem turned out to be leaky electrolytic crapacitors in the buck ...
18
votes
1answer
549 views

Soft-CPU verification

I'm currently in the process of designing a simple CPU in VHDL using Xilinx ISE and ISIM. The design portion is going remarkably well, but I can't seem to figure out a way to do verification in a ...
16
votes
1answer
550 views

Does anybody have any idea what this piece of equipment is?

A friend of mine picked this up at a garage sale where an elderly electrical engineer was selling a bunch of old test equipment. It's missing a faceplate where it should name what it is, and he's ...
15
votes
6answers
13k views

What is the difference between testing and verification?

Every textbook I've seen makes a big deal of the fact that testing and verification are two different concepts. Yet none of them provides a clear (or clear enough to me, at last) distinction. To ...
15
votes
6answers
3k views

What unit test framework can I use for a c based mcu project?

I'm thinking about how I can use unit tests in my mcu project, and what frameworks I can use to simplify it. Today I am using a stm32 with OpenOCD-jtag from a Linux pc, where it is all controlled ...
14
votes
1answer
1k views

Amateur radio practice exam question about voltage drop

So the question is as follows: ...
12
votes
3answers
41k views

What is Full form of hFE of a digital multimeter?

In digital multimeter, there is a transistor-check function, and there is a term hFE. I do-not know how-to use-it, however, different Websites say it is a measurement transistor's gain ("the ratio of ...
12
votes
4answers
26k views

How to test a crystal resonator in board?

I have 2 quartz crystal resonators in my pcb board: 32.768 kHz & 20 MHz. They are connected to a Freescale MC12311 transceiver IC, which has an HCS08 micro-controller embedded in it. I want to ...
11
votes
5answers
6k views

What parts would one typically use for automated PCB testing?

I have a circuit board in production, primarily through-hole, to the tune of ~400 units per year. Each one is manually inspected and tested. The board has ten distinct voltage rails, four voltage ...
10
votes
2answers
6k views

Continuity tests, risks?

Even though the electronic device is powered off, isn't there a risk of doing a continuity test on connections in the middle of the circuitry ? I mean, you do apply voltage doing so - couldn't that ...
10
votes
3answers
42k views

How to check if my multimeter's fuse is damaged?

I recently bought a cheap multimeter. I played around measuring stuff on simple circuits and I think I managed to damage it as I don't seem to be able to measure current anymore (always get zero ...
9
votes
3answers
3k views

SMD Crystal solder(?) problem and any recommended test procedure

I use a 32.768 kHz SMD crystal (datasheet) for a MCU. Here is the layout part of the crystal. Here is a view from an actual PCB I mounted the components by hand-soldering, and produced about 30 ...
9
votes
1answer
920 views

Verowire woes - how to reliably solder it?

I'm using Verowire (wiring pencil, Road Runner, you name it) quite often to contact test points on my board to make them accessible for measurements (oscilloscope probe, multimeter clamp ...) Image ...
9
votes
2answers
292 views

Calculate the resistances of all the possible connections inside a N-terminals black box based on measurements between terminals

Although it would seem that this is not the right SE for this thread since it is about creating an algorithm, the problem is actually about finding a systematic approach to the simplification of ...
8
votes
2answers
2k views

How do you identify Pin 1 based off these pictures? [closed]

This is a test question in a study book about electronics. I cannot find the answer and have no idea which picture identifies a pin. Am I missing something? Any help on the right answer along with ...
8
votes
9answers
18k views

Large difference between specced values and real values for LED strips?

Recently I bought some "300LED/5meter Waterproof 5630 SMD LED Flexable Strip" i.e. High brightness LED strips from China. In the specifications, it was said that the strip consumes 75W @ 12v, which ...
8
votes
4answers
41k views

How to find a faulty bulb in a Christmas lights string

I have a LED Christmas lights string, which consists of two circuits of LEDs connected serially. It is working directly on 110V AC. Most LED sockets have 2 wires connected to them, some have three. ...
7
votes
2answers
8k views

Designing a cable tester

I need to check the integrity of 40+ custom cables. Each cable is meant to be the same, and is meant to have 19 ways. I bought an enclosure, some mating connectors, some LEDS and a bunch of ...
7
votes
2answers
674 views

Testing an old Geiger tube?

I have an old Soviet personal radiation dosimeter that I broke as a kid by dropping it into water. I opened it up a while ago and the electronics in there were quite simple - mainly a ~10cm Geiger ...
6
votes
3answers
1k views

How low an insulation resistance is too low for a residential electrical system?

I have had occasion recently to test the wiring of a residential building for damage from a lightning strike. I opened all the breakers, removed all the loads, opened the panel, and meggered each hot ...
6
votes
2answers
53k views

How do I test a bridge rectifier?

I got a mess of components at an auction a couple weeks ago, including an unmarked box of unmarked bridge rectifiers. They're about 1" square & 1/4" high if that makes a difference in terms of an ...
6
votes
1answer
23k views

Can I test a USB port with a multimeter? [closed]

After a recent thunderstorm (Derecho), we had a power outage. After power restored, I noticed my desktop's USB ports (and a PS/2 port) were not responding, even at a BIOS level. Tried a known good ...
5
votes
2answers
1k views

How to test RF (1GHz) PCBs?

I have a number of RF PCBs. I would like to test these PCBs, so can someone guide me as to how to test these PCBs. The list of the PCBs that I want to test is mentioned below. 4th order Butterworth ...
5
votes
1answer
232 views

Intel 8042: what are “test inputs”?

I've implemented a driver for the Intel 8042 (keyboard controller in the IBM PC AT). The IBM 5170 (PC AT) Technical Reference served as my, well, reference for that. The output port and the test ...
5
votes
2answers
1k views

How do variable-frequency drives pass UL 508c failure of components testing?

Every 480V variable frequency drive I've had the pleasure of dissecting has had two DC capacitors in series across its DC bus, each rated for ~400VDC. UL 508c testing as executed on one of my recent ...
4
votes
3answers
786 views

How to test for USB dropouts on STM32F?

I've got a devices that is really strange, it drops USB periodically. By periodically I mean on a weekly (or biweekly) basis. By dropping out I mean windows loses the handle to the driver. Dropouts a ...
4
votes
5answers
1k views

Stress testing an FPGA's power supply

I have an FPGA (Xilinx Spartan 6) for which I want to stress test the power supply in "steps" (e.g. the FPGA runs in loops of 1 seconds: full steam for 900 ms, halted for 100 ms) to check that the ...
4
votes
2answers
889 views

What Would I Need Electrical Wire Testing Hooks For?

I want to buy accessories for soldering but was curious about electrical wire testing hooks: What are they for? For picking hard to access little wires? How do i work with them?
4
votes
4answers
5k views

Test Cases for 16-bit Ripple Carry Adder

I'm working on a lab for a course I have on VHDL, and part of it is to implement an n-bit ripple carry adder and then test it as a 16 bit adder. My problem is that I don't really know HOW to test it, ...
4
votes
2answers
301 views

Detachable “debug” portion of PCB?

I'm trying to add "optional" debugging test points to an existing, very dense 4 Layer PCB design (signal - GND - PWR - signal). I'd like to change the existing PCB as little as possible. My idea was ...
4
votes
8answers
6k views

Calculating current draw from a battery using voltage and time information

Is it possible to work out the current or power a device is drawing/using, based on the following information: Maximum capacity of a battery (48 Ah) A table of voltage readings over time (starting at ...
4
votes
2answers
2k views

Widlar current source

I need help solving this problem. I believe the current in the left side of the circuit equals the current in the right side. Therefore, $$K(V_{gs1} - V_t)^2 = 4K(V_{gs2} - V_t)^2$$ I also know \$V_{...
4
votes
1answer
390 views

CMRR test methodology and effect of open loop gain

I am trying to test the CMRR of opamp and so measuring offset variation across Common mode range in unity gain mode. I have gone through many articles on CMRR measurement. All those are suggesting a ...
3
votes
4answers
6k views

Methods to test/debug I2C protocols? [closed]

I've been working on some digital designs with I2C command & control and need a PC-based tool to test my interfaces. -- In the past, I've used iPorts (MCC) to do these tasks but the price tag of ...
3
votes
2answers
488 views

Why is my XNOR output always low?

I recently bought some Texas Instruments TTL chips. So far they've been OK, except the XNOR (SN74HC266N) chips (I've tried 3, including one that's never been in my "real" circuit) always output low ...
3
votes
3answers
455 views

What security risks does the Test Access Port (TAP) introduce?

Trying to get my head around the JTAG world I looked at how the Test Access Port (TAP) works and although I get why we need it, the diagram seemed to me (as a software developer) introducing some kind ...
3
votes
3answers
7k views

How to test TS7805 regulator if it is working?

I have a TS7805 voltage regulator that was placed on a pcb, laying around for 2 yeras. Is there a fast way to see if it is still working? I have a multimeter and some resistors at home and an DC 5-12V ...
3
votes
2answers
359 views

Measuring display brightness decay

Our device is specified to have a display brightness of 500 cd/m² and it must not decay to less than 50% brightness in 50,000 hours. Now, I can't wait for 5.7 years for that test to finish. I guess ...
3
votes
2answers
3k views

How can I test a hex Schmitt trigger?

Yay, me...I just got done soldering my first surface mount IC. Because I know how volatile heat can be, and with how close the tip of my iron was to the IC (especially without a socket!), I'd like to ...
3
votes
3answers
3k views

Applying load when testing battery voltage

Why do we need to apply a load to a battery, when testing its voltage? I've been testing battery capacity so far using a multimeter and just connecting the probes to the positive and negative side of ...
3
votes
3answers
2k views

How to produce a highly accurate phase or frequency shift at 500 MHz?

I currently have a couple of function generators that can be tied together in order to produce an arbitrary frequency or phase shift up to 20 MHz. Essentially I could say I want FN Generator 1 to be ...
3
votes
1answer
187 views

Giant pogo pin or spring probe pin for registration during electrical test

Solved: if you search for "GP-2 PCB Board Umbrella Shape 5.3mm Tip Testing Probe Pins Receptacles" you will find these probes! Thanks for the help! I am designing an electrical test fixture, and I ...
3
votes
1answer
1k views

How do you test SMD ICs that are not soldered to a PCB?

To be more specific, let's say I have SOP16 SMD chips that have been purchased from overseas. I have several PCBs that they need to be soldered to, but I don't want to risk paying for assembly and ...
3
votes
1answer
2k views

Cheap simple way to make an adjustable 1-10 MHz square or sine wave oscillator

For a test of a filter and video transmitter gear, I need a variable frequency (potentiometer adjusted) sine or square wave oscillator, adjustable from about 1 to 10 MHz. Output about 1Vp-p okay, but ...
3
votes
2answers
304 views

Please explain the circuit (current regulator test circuit with Zener diode)

my mind needs refreshing so could someone please help explaining analysis of this circuit. It is used for testing a current regulator (LED driver circuit) ('I' in the image). The regulator current is ...
3
votes
3answers
114 views

Should you Megger test transformers?

I have heard people say you shouldn’t Megger test transformers because the high voltages used might cause insulation between windings and between windings and the core to breakdown. Is this true? ...
3
votes
1answer
2k views

Test circuit for EU1640BCH12T / R Water proof ultrasonic sensors with Arduino?

I have EU1640BCH12T/R waterproof ultrasonic sensors, which I have got from this link. These are standalone raw sensors without breakout board and not a module like HC-SR04. Being a new electronics ...
2
votes
2answers
1k views

Test a transistor with a multimeter

I used the guide at https://vetco.net/blog/test-a-transistor-with-a-multimeter/2017-05-04-12-25-37-07 to test a transistor with my DMM. The NPN transistor I used to test is the "mospec tip130 No11D" ...
2
votes
4answers
2k views

Is it feasible to test microprocessor/microcontroller?

What I can do if I want to test the microcontroller?
2
votes
3answers
5k views

Testing an 8-ohm speaker

I have been trying to test an 8Ω speaker, but I am having some difficulties. I have tried to test the circuit using multisim using the circuit below: I used the 8Ω resistor in the place ...