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Test Equipment / Re: Fluke accuracy ±(2%+2) - What means the +2?
« Last post by boggis the cat on Today at 05:37:18 am »
A "fun" fact: I have seen a meter where the +number specification was worse than the % specification, even at full scale. I believe that this is sort of misleading. It was a ACV specification where the % was very good, but when adding the +number it was at best average (I do not remember the name of the meter).
That isn't uncommon for the very cheap instruments.  Sometimes you will see a change from +/- counts to +/- a value in order to try to be extra squirrelly.  Higher priced instruments will occasionally have this crop up in the margins, where they are presenting accuracy data (sometimes only 'typical') for end users that insist on using equipment beyond its real capabilities.

Beware of cut-down specification comparisons that only quote the % values (or other ratio).

Then there is the entire discussion over how realistic some accuracy claims may be.  (In general, the bigger name brands even amongst the cheap offerings are a lot more reliable.  No-name stuff is a bit of a lottery.)
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suggestions like "why you don't want auto range" is like when a guy asks - "Please help me with the directions to the post office?" and instead of directions he gets - "we need to know what is your problem, maybe a pub or strip club is the place where you should go?" :D

It seems that what you search for is a rare bird - I think people are trying to understand the "whys" so they might be able to give some suggestions that you might find useful even if they don't hit all the of check list items in the case that your target remains elusive.
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Your EPever IPower 5kW inverter is causing clock issues in your kitchen appliances due to frequency changes. Try adjusting the inverter settings or seeking advice from technical support could be beneficial.
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Test Equipment / Re: HP 3478A behavior on low ranges
« Last post by alm on Today at 05:04:10 am »
Yes, this is normal. Happens to pretty much every meter that is high impedance (GOhms) on the lower DCV ranges. This won't happen if it's actually measuring a signal with a finite impedance. Fix is to set it to a higher range where the input impedance is only 10 MOhm.
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Test Equipment / Re: HP 3478A behavior on low ranges
« Last post by bdunham7 on Today at 05:03:34 am »
Completely normal due to the small pias current (tens of picoamperes) charging up the input capacitance.  The resistance across the input is effectively nearly infinite.  Once you add 10M in parallel, the tens of picoamperes of bias current only result in hundreds of microvolts.
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I know no one likes post resurrecting, but this is still the number one hit for even tangentially related search terms!  So, since I’m using the 9616 (9615 with an interrupt line) and iso1640/iso1644s I figured I’d report that yes, the “output” i2c bus from a 9615/16 connected to side 2 of an iso1640/iso1644 does produce a nearly 0 voltage for Vol on side 1, just remember side one is “weak” with a max bus capacitance of 80pf which shouldn’t be a problem after the 9615, unless you’re just using it to traverse a long/noisy distance then have many devices on the other side.  Depending on your application, you may be able to buffer that with a lower static offset buffer (the 9615 is on the high end). Otherwise, the 9646 is the last remaining part from the 0 offset buffer product line…and it comes with a multiplexer… $6.62 in qty 10 from DigiKey.  Ouch.  Only a little more expensive than the iso1644. 

If anyone has any other parts that kill static voltage offsets on i2c I’d love to hear about them…and so would anyone else searching for very similar terms!
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Projects, Designs, and Technical Stuff / Re: Different die pictures
« Last post by Noopy on Today at 05:00:37 am »


The Intersil ICM7226A is a fully integrated frequency counter that can determine frequencies up to 10MHz. The component with index A is designed to drive 7-segment displays with a common cathode. The ICM7226B, on the other hand, drives 7-segment displays with a common anode.




The test circuit in the datasheet shows how efficiently the ICM7226 is constructed. The module contains an oscillator and directly drives eight 7-segment displays. The outputs, which multiplex the individual digits, are used simultaneously to read in the function selection and the counting range.




The ICM7226 datasheet contains a detailed block diagram showing how the chip does the counting.




The dimensions of the die are 4,3mm x 4,1mm. The image is available in original size: https://www.richis-lab.de/images/counter/01x03XL.jpg (29MB) It can be seen that the design would provide two additional bondpads. However, these bondpads are not metallised, so they can only be used when a different metal layer is used.

The lowside transistors, which control the segments of the active 7-segment display, are located at the top edge. The highside transistors, each of which activates one of the 7-segment displays, are located in the bottom left-hand corner. Repeating structures can be recognised in the core of the ICM7226. The majority of these areas are likely to contain frequency dividers, of which a large number is required.




Test structures are integrated in the top right-hand corner. Next to them are character strings that could be the initials of the developers, among other things.




The revisions of six masks can be seen in the bottom right-hand corner. The designation ICM7226 is shown underneath. Y appears to be the revision of the design. The Y appears several times on the die. If we assume that we are counting backwards from Z, then this is a second revision.

A closer look reveals that a 1 is depicted in a lower position in place of the second 2. This indicates that the design could be used for both the ICM7226 and the ICM7216. All you have to do is change the metal layer.




The ICM7216 offers slightly fewer interfaces due to its smaller housing, in particular the BCD output is missing. Otherwise it is the same module. It therefore makes sense to operate the ICM7216 and the ICM7226 with the same circuit.


https://www.richis-lab.de/counter01.htm

 :-/O
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Test Equipment / HP 3478A behavior on low ranges
« Last post by radar_macgyver on Today at 04:57:07 am »
I have an HP 3478A that shows a slowly increasing count on lower DC volts ranges (anything less than 30V). Eventually, it goes overrange, and starts faintly beeping and zeroes itself, then repeats the cycle. Any resistance applied between the probes (I tried several 1M resistors in series) will bring the voltage back to zero, as will putting it into the 30 or 300V range. I suspect the latter is due to a voltage divider. Is this normal behavior?

The instrument has not been used in many years (possibly decades), I cleaned it out with compressed air but am afraid to use any solvents after seeing the weird hybrid inside. I also need to replace its cal battery... it measures about 1.2V, and it somehow is still calibrated!

Fun fact: it was actually a prototype unit (the son of a former colleague used to work at HP and was apparently on the design team). Some folks from Keysight visited our lab and I showed it to them, they remarked that the missing front badge and no serial number was a good sign it was indeed a prototype.
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Repair / Re: SIP compressor won't start?
« Last post by Swainster on Today at 04:56:25 am »
There is a suspicious mark by the overload switch. Speaking of overload switches, I had one fail on a cheap compressor - it's worth checking if yours is working properly
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Beginners / Re: Getting started with microcontrollers
« Last post by radiolistener on Today at 04:56:02 am »
Heck, I’m not a beginner and I have no clue what most of that code does!

Are you kidding? Common dude, the code is pretty clean.
It may scary for you just because it uses some new syntax which is not familiar for you, but that can be learned within several hours.

Just look, the structure is very transparent:

First we declare which libraries and featrues we will use:
Code: [Select]
// std and main are not available for bare metal software
#![no_std]
#![no_main]

extern crate stm32f1;
extern crate panic_halt;
extern crate cortex_m_rt;

use cortex_m_rt::entry;
use stm32f1::stm32f103;

Then we have main code:
Code: [Select]
#[entry]
fn main() -> ! {
...
}

which consists of two parts, first part is initialization:
Code: [Select]
    // get handles to the hardware
    let peripherals = stm32f103::Peripherals::take().unwrap();
    let gpioc = &peripherals.GPIOC;
    let rcc = &peripherals.RCC;

    // enable the GPIO clock for IO port C
    rcc.apb2enr.write(|w| w.iopcen().set_bit());
    gpioc.crh.write(|w| unsafe{
        w.mode13().bits(0b11);
        w.cnf13().bits(0b00)
    });

and the second part is main loop:
Code: [Select]
loop{
        gpioc.bsrr.write(|w| w.bs13().set_bit());
        cortex_m::asm::delay(2000000);
        gpioc.brr.write(|w| w.br13().set_bit());
        cortex_m::asm::delay(2000000);
    }

There is even no need to know Rust to read the code and say what it does, it self explaining...

The only thing which may be not obvious are these manipulations for GPIO port configuration. But this is not Rust specific thing, this is MCU specific details, which will be the same for any language. You're needs to read MCU datasheet in order to learn it.
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