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I had the same problem and I called the factory and was told to push set and mode at the same time after display comes on this then will say fac off. Its turns the compensation mode off

Send them back to Russell, I am sure he will take care of it.

Originally Posted by hvac5646

I'm ready to put mine on Craigs list. They just wont stay in calibration on temp clamps.

Originally Posted by lytning

%70's are great, BUT I find that I use the Sman4's more.

I'm ready to put mine on Craigs list. They just wont stay in calibration on temp clamps.

%70's are great, BUT I find that I use the Sman4's more.

Originally Posted by hvac5646

Naw, man. You need the 570 with all accessories.

Originally Posted by hvac5646

Naw, man. You need the 570 with all accessories.

For sure see one in my future.Still trying to figure this one out..

Originally Posted by keithmylum

Good stuff to know. Just got mine. Sure makes me sleep better at night knowing I can trust my gauges.

Naw, man. You need the 570 with all accessories.

Good stuff to know. Just got mine. Sure makes me sleep better at night knowing I can trust my gauges.

Originally Posted by Vettgetsmwet04

ive used my testo 550 for about a month now, u have to make sure that the liquid line and suction line u clamp onto is perfectly striaght or the readings will be off, if the pipe is straight and u have the probe making good contact then its perfectly accurate compared to my fluke clamps and my fieldpiece probes, ive compared over and over, if its off its because the copper is slightly bent or i didnt have the probe saddled on there right.

now on my two clamps i leave them plugged in all the time, i have a spot on my truck thats padded and i hang them them away from other things so nothin bothers them. i was finding that if u touched either clamp it would move off the copper pipe and lose good contact, so i decided to make the clamps better, i took my smallest step bit and on the clamp for the liquid line i drilled the side opposite of the senser on the clamp until i almost made a semicircle, about the same size and 3/8 copper, this makes it to where as long as the copper is striaght, it will make good contact and not move off even if it gets hit, i did the same with the suction clamp, but with a bigger sized step bit and not as dip, but just pushed down on it and drilled it out until a 7/8 pipe would fit on it good. and the ease of use is now much better, just as long as the copper is clean and striaght.

i do 90% resi and 10% commercial, so i rearly see anything over 7/8 and 3/8, sometimes 1 1/8 but not much, but if your like me do this and the clamps will saddle the copper much better for better results.

It took 10-15 minutes for them to all agree, but this is not practical on a working unit that is fluctuating either degrees or tenths of a degree.

ive used my testo 550 for about a month now, u have to make sure that the liquid line and suction line u clamp onto is perfectly striaght or the readings will be off, if the pipe is straight and u have the probe making good contact then its perfectly accurate compared to my fluke clamps and my fieldpiece probes, ive compared over and over, if its off its because the copper is slightly bent or i didnt have the probe saddled on there right.

now on my two clamps i leave them plugged in all the time, i have a spot on my truck thats padded and i hang them them away from other things so nothin bothers them. i was finding that if u touched either clamp it would move off the copper pipe and lose good contact, so i decided to make the clamps better, i took my smallest step bit and on the clamp for the liquid line i drilled the side opposite of the senser on the clamp until i almost made a semicircle, about the same size and 3/8 copper, this makes it to where as long as the copper is striaght, it will make good contact and not move off even if it gets hit, i did the same with the suction clamp, but with a bigger sized step bit and not as dip, but just pushed down on it and drilled it out until a 7/8 pipe would fit on it good. and the ease of use is now much better, just as long as the copper is clean and striaght.

i do 90% resi and 10% commercial, so i rearly see anything over 7/8 and 3/8, sometimes 1 1/8 but not much, but if your like me do this and the clamps will saddle the copper much better for better results.

I have to agree with Mark on the lack of confidence that the 550 temp probes provide.

I just received a replacement unit from TTT and the probes are anywhere from even( on a piece of copper sitting on my dinning room table) to 4*-5* different on the same pipe and way slooooooooooow to react!

Originally Posted by jvillehvac

I didnt say mine were different than his, did I? As with any other mass produced product you plan on them reading the same. Real world, who knows. How do we know all that other stuff on there is right, oh thats right, digi cools and flukes are never out of calibration! I already tried all this when I first got mine 2 months ago cause like him I didnt want to blindly trust a new tool. Why mine arent off I dont know, go ask a testo engineer and let me know.

Well, when 6 different probes in 6 different instruments using 3 different technologies from 3 different manufacturers are all within a degree or so of each other, and 2 probes in another instrument give readings that vary significantly from the other instruments, and from each other, guess which probes I'm calling into question.

I don't doubt the accuracy of the 550 or its probes.
When I have all that mess clamped on a piece of copper in my living room or garage, everything in those pictures, including some additional air temp probes and instruments, all of it, except the Fluke clamp I pulled out of my junk drawer, the difference between the lowest and highest readings displayed on any of the instruments is less than 1ºF.

The problem I'm having with the probes for the 550 is getting precise readings when there is a significant difference between ambient temperature and the pipe temperature, especially when there is not an absolutely straight section of pipe to clamp the probe to, which is the norm with residential equipment.

Accuracy is not the same as precision, they are related, but still 2 different things.

Originally Posted by itsiceman

Really close to what? If they all read the same equalized and at rest at Marks house what could be different about yours and his clamps

I didnt say mine were different than his, did I? As with any other mass produced product you plan on them reading the same. Real world, who knows. How do we know all that other stuff on there is right, oh thats right, digi cools and flukes are never out of calibration! I already tried all this when I first got mine 2 months ago cause like him I didnt want to blindly trust a new tool. Why mine arent off I dont know, go ask a testo engineer and let me know.

Originally Posted by jvillehvac

mark, im wondering if you got some bum 550 clamps or something. whenever i compare mine they are really close. i must admit i dont have that many instruments and if i did that in my house my wife would think im crazy!!!

Really close to what? If they all read the same equalized and at rest at Marks house what could be different about yours and his clamps

mark, im wondering if you got some bum 550 clamps or something. whenever i compare mine they are really close. i must admit i dont have that many instruments and if i did that in my house my wife would think im crazy!!!

I used a set of 550 's today. I also placed a Fluke 52 with their 80pk (not sure of the number) quick clamp probe next to the Testo probe. Virtually no real difference. The Fluke read 1.3º lower; Fluke was last calibrated 10 yrs ago. Close enough for me. BTW: after reading about some 'problems" witht he Testo probes, I could not find any. I did make sure that the tubing was clean of junk and straight.

Mark on the 550 clamp that you're working on you might try to pull that sensor into the clamping pad area 1/4" or so.
I am only guessing but think some of that metal jacket on the cord end is to conduct to the wire itself and the actual tiny sensor inside there is located closer to the tip that is dead ended anyway. May help with centering also having the sensor closer to the middle of the clamp pad as well.

Also comparing the 523's gets funny at a point.
The time I've seen a difference like that or greater there is a difference like that where you have them mounted
(temp of the pipe and temp of the room ambient)
Is that the PT-100 Clamp on top of all those sensors there LOL

Decided to hook most of my pipe temp stuff up, just for grins.

The instruments.


The probes. One of the Testo 550 probes has some slight temporary improvements.


1st and 2nd gen 523's


2 Digi-Cool DRSA-1250's.


Note the difference in the 2 temps on the 550. This is after fussing with the probes a lot to get the max reading I could get.
The higher of the 2 is the probe with the orange weather strip on it.
The probe in the Fluke 52 on the left, and the Testo probe in t2 of the Fluke 52 on the right are the probes I use, the other is out of my junk drawer.

Originally Posted by itsiceman

This NTC thermistor looks small in perspective to me and better contact than a bead type thermocouple

That's pretty tiny!
I haven't seen a NTC thermistor probe available that uses a sensor that small. Usually they are pretty big, like the ones Cooper, Testo and Digi-cool use.

I don't use bead type thermocouples. I use probes that have ribbon thermocouples in them, like the Fluke 80pk-8, and the Testo 0602 4592 pipe clamp thermocouple probe (expen$ive) for larger pipe sizes, and my Fluke surface probe. The nice thing about ribbon thermocouples is that they are wafer thin, the actual sensing portion is very small and has almost no thermal mass, and they will conform somewhat to the shape of the pipe, so it doesn't really matter if you don't have a perfectly straight section of pipe to hook the probe up to. They will work just as well on the inside or outside of a slight bend as they will on a perfectly straight section of pipe.
Good probes that use ribbon thermocouples fight tightly to the pipe, have a solid "in the correct position feel", and back up the sensor with a dead air space.

IMO, what a good quality ribbon type thermocouple lacks in raw accuracy vs a NTC thermistor, it more than makes up for in the ability to get a precise reading in less than perfect conditions in the field. There is also the issue of timeliness of the information displayed. My thermocouples react almost instantly to line temperature changes, The sensor in the typical NTC thermistor prob just can't react that fast.

Originally Posted by mark beiser

True, but when you get down to finished products, NTC thermistor probes virtually always have many times the thermal mass, and require much more contact area than a thermocouple or high end PT100 probe.

This NTC thermistor looks small in perspective to me and better contact than a bead type thermocouple