I have one of the kickstarter meters and would be happy to check some things out on it. But only be able to get to it on a weekend.
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I'd replace these 1N4007 by reversednpn transistors, as these usually have very low leakage current, as already being used similarly in the 121GW, i.e. Q1, Q2 (n.a.), Q3, Q5.n-JFETs. Used as diodes, these have low leakage, but also high breakdown voltage (which the E-B diode of npns don't have), as 15V may be present there.
One problem is that hundreds of meters have been shipped, but very few people are commenting in this thread or reporting their experiences with their meters. As Joe said, it is almost as if everyone has just put them on a shelf in their boxes for posterity.
So trying to find a pattern is very difficult with such a small sample size.
...
As for logging, if the spikes were real I would want to see them but they are not. I don't see a problem like this with even the cheapest logging meters I have when sampling at the same rates. I really can't think of a time where I have needed a handheld meter to record faster than a second. In most cases, even that is fast. If I am need to see faster changing signals, I am using something else to collect the data. For me, what ever I collect, I want the data to be accurate first and foremost. If the meter is not the right tool for the job because of it's speed, I will use another tool.
I saw 13 spikes in 15 minutes at 5Sa/s, with the spikes taking at least 3 samples, thats 1% of the samples corrupted.
I saw 13 spikes in 15 minutes at 5Sa/s, with the spikes taking at least 3 samples, thats 1% of the samples corrupted.
I saw a spike when measuring DC mV directly (the green trace below just after 100 s). At the time I thought it might have been some external influence. It didn't occur to me that the meter itself might have introduced the artifact. That's interesting.
Hand proximity tests using various configurations with firmware 1.0.
https://youtu.be/s7QVwFXmxgQ
Thanks for this update. Good to hear they are working on it. What ever their reason for this change, it could have an added advantage if they pick the parts right. U9 is the first thing to get damaged in my testing. I am using a TVS rather than the 4007s to protect it and swapped the HEF4053 for a CD4053. It held up pretty good after that.
I also have to comment that if the software was truly open source (or hacked to be) as I thought when I purchased the meter I might be more inclined to get into the discussion.
The bugs like not defaulting to the default scale is more "serious" imho.
The bugs like not defaulting to the default scale is more "serious" imho.
What bug is that?
Select a position. E.g. V DC. Press Mode to change it in AC. Turn off the meter and on. Select again V. It remembers the AC mode selected.
One scenario is that you try to measure a high DC or AC voltage and the meter is in the other mode. It will show 0...
Hi,
I think I found another design issue in the meter circuit.
I wanted to find out whether the meter can be used with lithium batteries instead of standard cells or not.
Problem with lithium cells ist the higher voltage. 4 lithium cells have up to 7.7V when they come out of the package. After a short time the voltage goes back to approximate 7 V and stays a long time at this value.
Problem or not?
I could not find any hint to this question, so I started to explore the schematics.
First it looked good, all internal voltages came from low drop regulators.
+4V, VDD(3.3V) analog supplies and VDD_P (3.3V) for the 15V booster and the CPU.
So, no problem at all, none of the voltages can go to high.
But wait, what is that?
The voltage reference, ZD1, a ADR3412 reference regulator is connected directly to B+ via R94, a 0 ohm resistor. B+ is the battery voltage. And this is a problem in my opinion. According to the datasheet the input voltage range of the ADR3412 is 2.3V..5.5V, the absolute maximum is 6V.
That means even with alkaline batteries the voltage is above the input range and with new alkaline batteries also above the absolute maximum. With lithium cells it is way off from the allowed input voltage.
Populate R12 instead of R94 will supply the reference with +4V, so no problems in this configuration. But R94 is populated, not only in the schematics. I have checked this in my meter and actually R94 is populated. I will remove R94 and place it in the R12 position.I cannot understand why the reference is connected to B+, that makes no sense for me. Is this really a design flaw or did I overlook something?
I also have to comment that if the software was truly open source (or hacked to be) as I thought when I purchased the meter I might be more inclined to get into the discussion.
Sorry anyone thought the meter would be open source firmware, that was never promised.
The schematic is available, the PC software is fully open source, and the protocols are open.
We'll fix the manual.
Bug solved!
Alexander.
Hi,
I think I found another design issue in the meter circuit.
I wanted to find out whether the meter can be used with lithium batteries instead of standard cells or not.
Problem with lithium cells ist the higher voltage. 4 lithium cells have up to 7.7V when they come out of the package. After a short time the voltage goes back to approximate 6.6V and stays a long time at this value.
Problem or not?
I could not find any hint to this question, so I started to explore the schematics.
First it looked good, all internal voltages came from low drop regulators.
+4V, VDD(3.3V) analog supplies and VDD_P (3.3V) for the 15V booster and the CPU.
So, no problem at all, none of the voltages can go to high.
But wait, what is that?
The voltage reference, ZD1, a ADR3412 reference regulator is connected directly to B+ via R94, a 0 ohm resistor. B+ is the battery voltage. And this is a problem in my opinion. According to the datasheet the input voltage range of the ADR3412 is 2.3V..5.5V, the absolute maximum is 6V.
That means even with alkaline batteries the voltage is above the input range and with new alkaline batteries also above the absolute maximum. With lithium cells it is way off from the allowed input voltage.
Populate R12 instead of R94 will supply the reference with +4V, so no problems in this configuration. But R94 is populated, not only in the schematics. I have checked this in my meter and actually R94 is populated. I will remove R94 and place it in the R12 position.I cannot understand why the reference is connected to B+, that makes no sense for me. Is this really a design flaw or did I overlook something?