Logic Probe that measures HI Z impedance

[danny davis]

Which Logic Probe measures HI Z impedance

I can't find one that will display or measure HI Z impedance

Do these? or where can I find one that does?

https://www.amazon.com/Precision-DP...F8&qid=1389064772&sr=8-9&keywords=Logic+Probe

https://www.amazon.com/RSR-LOGIC-PR...8&qid=1389064907&sr=8-14&keywords=Logic+Probe

https://www.amazon.com/Elenco-Elect...8&qid=1389064973&sr=8-1&keywords=Logic+Probes

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Multi-meter Pens have a logic setting, but do they measure the HI Z logic level?

I think they are better than logic probes because they can display the logic voltage level, you can see the voltage display , a logic probe you don't know what HIGH or LOW voltage you have when during with CMOS can go from +5 volts to +22 volts for a High, so an Multi meter pen can display this information

http://www.amazon.com/Range-Pen-Type-Digital-Multimeter-MS8211D/dp/B000E8EYOQ/ref=sr_1_7?ie=UTF8&qid=1389065164&sr=8-7&keywords=Logic+Probe

http://www.amazon.com/Dawson-DDM190D-Pen-Type-Digital-Multimeter/dp/B008ALRB6C/ref=sr_1_6?ie=UTF8&qid=1389065201&sr=8-6&keywords=Logic+Probe

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Some logic probes have a MEMORY option button
This is for freezing logic states that are logic signals in the nanoseconds or a quick pulse or trigger signals

What else can u use the Logic Probe Memory option button for?

 

[Audioguru]

Re: Logic Probe That measures HI Z impedance

Why do you want to measure high impedance logic levels? What produces high impedance logic levels?
TTL doesn't. Cmos doesn't. Transistors don't. Mosfets don't.
Instead, maybe you want to detect a floating output when it is active on a tri-state output? A floating output does not have a logic level.

You are WRONG when you say that Cmos logic levels are unknown when the supply voltage has a wide range. The circuit should have a FIXED supply voltage and the datasheet for the logic family says the voltage ranges that are high and low for each supply voltage. The logic probe should know this if it can sense the supply voltage.

 

[danny davis]

Re: Logic Probe That measures HI Z impedance

maybe you want to detect a floating output when it is active on a tri-state output?

Yes which logic probe detects a floating output and tri state output

Which one does this?

Do these? or where can I find one that does?

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You are WRONG when you say that Cmos logic levels are unknown when the supply voltage has a wide range. The circuit should have a FIXED supply voltage and the datasheet for the logic family says the voltage ranges that are high and low for each supply voltage. The logic probe should know this if it can sense the supply voltage.

The Logic probe doesn't tell you if your CMOS LOGIC HIGH is a +5 volts, +10volts, +15 volts, +22 volts

It just turns on a LOGIC high Red Light , doesn't tell u what logic high voltage you have

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http://www.amazon.com/Elenco-Electronics-LP-560-Logic-Probe/dp/B000Z9HAP4/ref=sr_1_1?ie=UTF8&qid=1389071305&sr=8-1&keywords=logic+probes

http://www.amazon.com/Precision-DP52-Digital-Logic-Probe/dp/B009D6O4X6/ref=sr_1_9?ie=UTF8&qid=1389071338&sr=8-9&keywords=logic+probe

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Why do you want to measure high impedance logic levels? What produces high impedance logic levels?
TTL doesn't. Cmos doesn't. Transistors don't. Mosfets don't.

You're wrong:

The tri-state output is a high impedance state in which the output pin has no value (it is not at logic 0 and not at logic high, you can think of this state as infinite impedance).

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This logic probe circuit has 3 LEDS for the Hi Impedance Tri state

http://www.eleccircuit.com/many-logic-probe-circuit-ideas/

When the logic probe is either connected to an invalid logic level (a fault condition or a tri-stated output) or not connected at all, none of the LEDs lights up.

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How do you know if the signal is an OPEN? or a LOW state? or a Tri-state?

Can I use my ohm meter to measure the resistance of the output pin or input pin to know if it's an OPEN state or Tri-state? or Low State?

 

[Audioguru]

Re: Logic Probe That measures HI Z impedance

If you want to detect an output that is floating and is tri-stated then use a logic probe that detects it. It is not a high impedance "logic level" that you asked about.

The datasheet for a CD400x shows its allowed input voltages:
1) With a +5V supply its logic low is 0V to +1.5V and its logic high is +3.5V to +5V.
2) With a 10V supply its logic low is 0V to +3V and its logic high is +7V to +10V.
3) With a +15V supply its logic low is 0V to +4V and its logic high is +11V to +15V.
If your logic probe does not use this information then it is WRONG and maybe its owner's manual states that it is accurate ONLY when the supply is +5V.

 

[danny davis]

Re: Logic Probe That measures HI Z impedance

If you want to detect an output that is floating and is tri-stated then use a logic probe that detects it.

That's what I'm asking, WHICH logic probe detects floating and Tri stated? which one so i can order it

Using an Ohm meter can I measure the ohms of the tri state or floating? it should be in the meg ohms right?

A low state is at what ohms?
A high state is at what ohms?
A Tri state is at what ohms? MEGS?
Floating state is at what ohms? MEGS?

 

[Audioguru]

Re: Logic Probe That measures HI Z impedance

That's what I'm asking, WHICH logic probe detects floating and Tri stated? which one so i can order it

Sorry, I do not have time to look up their spec's.

Using an Ohm meter can I measure the ohms of the tri state or floating? it should be in the meg ohms right?

I never looked and I do not want to look. Why don't you look at the datasheet of the ICs you work with that have tri-state outputs?

A low state is at what ohms?
A high state is at what ohms?
A Tri state is at what ohms? MEGS?
Floating state is at what ohms? MEGS?

They are listed as voltages and currents on the datasheets. You can use Ohm's Law to calculate ohms.

 

[danny davis]

Re: Logic Probe That measures HI Z impedance

I never looked and I do not want to look. Why don't you look at the datasheet of the ICs you work with that have tri-state outputs?

It's not about the IC having an Tri-state output,

It's also about when IC have an OPEN output caused by damage, how can I measure this? do i use an ohm meter for this?

I'm trying to measure IC inputs and outputs to KNOW if they are an OPEN caused by damage? , what would it measure or how would u measure this?

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That's what I'm asking, WHICH logic probe detects floating and Tri stated? which one so i can order it
Sorry, I do not have time to look up their spec's.

I can't find a Logic Probe that Tells you it detects a floating or Tri state output

I think the Logic Probes DON"T Light only when it's a floating or Tri state output , but not sure if ALL logic probe do this detection

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Logic Probe with MEMORY

1.) Is for measuring pulses that are in the NANOSECONDS
2.) to measure Signal fast events or triggers

I still don't get it, the HIGH state light will blink

But how does this tell you anything? big deal that it stores the HIGH state, does that tell you anything?

How do you know if the pulse is in the nanoseconds, and how do you know it's a single event or trigger?

 

[Audioguru]

Re: Logic Probe That measures HI Z impedance

Why do you not know what the output of a logic circuit is supposed to do (its spec'd output high voltage and maximum current and its spec'd output low voltage and maximum current? They are listed on their datasheet and they are simple to measure.

It is obvious that when its output voltage is supposed to be high but it is not or its output high voltage should have a certain maximum amount of current but its is not then its output is blown. It is also obvious that when its output voltage is supposed to be low but it is not or its output low voltage should have a certain maximum amount of current but its is not then its output is blown.

Please find a logic probe yourself. You will not learn how to use it and you do not know what is a good measurement or what is a bad measurement anyway.

 

[danny davis]

Re: Logic Probe That measures HI Z impedance

It is obvious that when its output voltage is supposed to be high but it is not or its output high voltage should have a certain maximum amount of current but its is not then its output is blown. It is also obvious that when its output voltage is supposed to be low but it is not or its output low voltage should have a certain maximum amount of current but its is not then its output is blown.

How does a logic probe, tell you that a input or output is BLOWN?

is it a shorted input or output or an OPEN blown input or output? a logic probe doesn't tell u that

A logic probe doesn't input input and output pin measure current or does it?

 

[Audioguru]

Re: Logic Probe That measures HI Z impedance

How does a logic probe, tell you that a input or output is BLOWN?

A Cmos input uses NO current so how can a logic probe know if it is blown? a logic probe should be able to detect normal or abnormal input current for a TTL input.
The input voltages also have a range that must be correct.

is it a shorted input or output or an OPEN blown input or output? a logic probe doesn't tell u that

A logic probe cannot detect that a Cmos input is blown. It can detect a blown TTL input. But it can detect a shorted Cmos or TTL input.
A logic probe should be able to detect an open or shorted output.

A logic probe doesn't input input and output pin measure current or does it?

Very bad English.

 

[danny davis]

Re: Logic Probe That measures HI Z impedance

A Cmos input uses NO current so how can a logic probe know if it is blown?

Right , so HOW would u do to test a CMOS blown input? using what?

and what would it measure when a CMOS input is blown

Wouldn't an Ohm meter measure in the Megs ohms when a CMOS input is blown?

a logic probe should be able to detect normal or abnormal input current for a TTL input.

So a logic probe has a current sensor circuit that detect abnormal input current for a TTL input?

It can detect a blown TTL input.

What does the Logic probe do when it detects a blown TTL input? NO LIGHTS ? is it blown or floating or OPEN , how can you know?

But it can detect a shorted Cmos or TTL input.

What does the Logic probe do when it detects a SHORTED CMOS OR TTL input? NO LIGHTS ? is it shorted or Blown or floating or OPEN , how can you know?

NO LIGHTS can mean any of these:
1.) SHORTED INPUT or output
2.) BLOWN input or output
3.) FLoating input or output
4.) Tri-state input or output
5.) OPEN input or output

ALL 5 of these will produce NO LIGHTS on the logic probe, so how can you tell please?

How can a electronic technician know which one is the problem or what is damaged to the IC chip? how can I verify this?

 

[danny davis]

Re: Logic Probe That measures HI Z impedance

Is there another way besides using a Logic Probe to measure and VERIFY that a logic IC chip is
1.) SHORTED INPUT or output
2.) BLOWN input or output
3.) FLoating input or output
4.) Tri-state input or output
5.) OPEN input or output

How can I VERIFY this? using what and how do i measure this please to Verify these 5 different malfunctions?

 

[Audioguru]

Re: Logic Probe That measures HI Z impedance

Danny, the answers to your latest questions are so simple that I will not talk about them anymore.

Oh, you are not allowed to replace a defective IC unless you say what failed on it? Since you did not design the failed IC then you are simply guessing what failed in it. Does it matter how it failed?
Oh, somebody worries that the replacement IC will fail the same way and the very old circuit must be re-designed to prevent it?

I worked with a new very expensive Japanese product. The owner of the huge company that bought the first one was worried that its power supply was very hot. The Japanese manufacturer said it will be fine. It and others failed the next week.

 

[danny davis]

Re: Logic Probe That measures HI Z impedance

U have to explain the failure and malfunction with iso9000 forms in detail thats why, help me out i

 

[Audioguru]

Re: Logic Probe That measures HI Z impedance

You have a CD4069 inverter with an output always low. When the input goes low then the output should go high but it doesn't.
1) Is the output shorted to ground?
2) Is the input shorted to the positive supply?
3) Is the input blown?
You can turn off the power supply and measure low voltage ohms on #1 and #2 to measure a short or not but since Cmos has no input current then you will never know if the input is blown.

Why do you ask about a floating input? There is no such state. A blown input will be floating because its connection is blown. But you will never know if the input is blown or if a connection inside the IC is disconnected.

Why do you ask about a tri-state input? No such thing. Tri-state is only used on a tri-state output.

Why do you ask about an open input? What will you measure? A Cmos input has no current so there is nothing to measure even when nothing is wrong with it.

What is the difference between a blown output or a floating output or a tri-state output that is made high impedance or an open output? Wouldn't they all measure the same?

 

[betwixt]

Re: Logic Probe That measures HI Z impedance

Danny, ask yourself this: if a point in a circuit is hi impedance, what difference would you expect a logic probe to show when connected to it compared to if you didn't connect the probe at all.

I remember an ISO fault report concerning a mis-inserted IC, the reason for failure was written as "operator mounted with leg underneath". And no, it wasn't a medical product. :-D

Brian.

 

[Tunelabguy]

Re: Logic Probe That measures HI Z impedance

1.) SHORTED INPUT or output
2.) BLOWN input or output
3.) FLoating input or output
4.) Tri-state input or output
5.) OPEN input or output

ALL 5 of these will produce NO LIGHTS on the logic probe, so how can you tell please?

How can a electronic technician know which one is the problem or what is damaged to the IC chip? how can I verify this?

You verify what is wrong by first understanding your circuit.

 

[danny davis]

Re: Logic Probe That measures HI Z impedance

if a point in a circuit is hi impedance, what difference would you expect a logic probe to show when connected to it compared to if you didn't connect the probe at all.

It could be any of these

1.) SHORTED INPUT or output
2.) BLOWN input or output
3.) FLoating output
4.) Tri-state output
5.) OPEN input or output

How can you verify , test, check these different malfunctions?

When Logic Signals are BELOW ground, - 5 volts, - 10 volts, - 15 volts, what is this type of logic called? it's not called negative logic

 

[danny davis]

Re: Logic Probe That measures HI Z impedance

It could be any of these

1.) Logic low = Zero volts
2.) Blown output = zero volts
3.) Floating output = zero volts
4.) Tri state output = zero volts
5.) Open output= zero volts
6.) Shorted output to ground = Zero volts

How can I verify which is which if they are all zero volts?

I can't tell the difference because my DVM meter or O-scope is at zero volts when I'm measuring Logic Gates, latches, flip flops, etc. so is it a logic low? Blown output? Floating output? Tri-state output? open output? shorted output? because they all can be ZERO VOLTS , so how can you tell please?

How can you verify , test, check these different malfunctions?

How do I know if the output pin is shorted to ground when it's zero volts? zero volts can be a logic low so you might think the IC chip is working
How do I know if the output pin is Open , when it's measuring zero volts? zero volts
How do I know if the output pin is Tri State output and it's working?, when it's measuring zero volts? it can be shorted to ground , or open because any of these options will measure zero volts


When Logic Signals are BELOW ground, - 5 volts, - 10 volts, - 15 volts, what is this type of logic called? it's not called negative logic

 

[danny davis]

Re: Logic Probe That measures HI Z impedance

I think for measuring the floating output, you have to measuring it using an OHM meter, not a volts meter to verify that the Tri-state is Hi impedance, you can't measure the voltage of a Tri-state logic because it's NOT a voltage it's a resistance right?