I have a specific PicoScope question I have ask of the US distributers and Pico UK and have not been able to get my question understood. Is there an e-mail address I can use to communicate with Paul Danner?
I have a secondary e-mail address that you can reply to so we can communicate privately.
<gibbsbrand@gmail.com>
Thank You
I have a question on the Pico WPS600 Hydraulic Pressure Transducer. I am suspicious that the pressure reading can be easily manipulated by turning on the transducer and self-zeroing the transducer with a vacuum applied to the transducer and then removing the vacuum from the transducer and allowing atmospheric air pressure (0 gauge pressure) to stabilize within the transducer. Could this cause the PicoScope to read a positive pressure with no pressure applied to the transducer? You are actually adding pressure to your actual reading.
I am greatly impressed with your knowledge and use of the PicoScope as a diagnostic tool. What I am in search of is someone with a PicoScope that can diagnose the tool. Would you offer a service to do this diagnosis of the equipment? I would like you to take a WPS600 Transducer, if you don't have one I can buy one and bring it to you, and apply a vacuum from a hand vacuum pump to the transducer, then power up the transducer allowing it to self-zero under a vacuum. Then remove the vacuum from the transducer and see if the Pico reads a positive pressure with nothing hooked to the transducer.
I have asked this question of the US distributers and Pico of the UK. But I don't think they understand my question. They offer very sophisticated equipment to give an accurate reading and they can't seem to understand why anyone would want anything less. I had a shop try to falsify their reading to cover up some bad work they did for me.
Please let me know if you can help confirm my suspicion.
Of course it wiil as you describe it the software in a normal setup zeroing to datum ambient pressure is required to read a true gauge pressure. Artificially setting the zero to above or below ambient pressure will change the datum skew the readings by a constant amount as in Y=MX+C . But how much " correction" can be added or subtracted from the datum will probably be limited by design in the software and the sensor will of course have its own limits.
The burning question is why ask the question?
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Thanks Andy,
My problem is that I had a farm tractor engine completely overhauled at my local CaseIH dealer. The tractor was delivered after the overhaul with less oil pressure than when it left. The failure was coolant in the oil from wet cylinder sleeves that leaked coolant in the oil with the engine not running. I lucked out with no internal damage from running the engine with coolant in the oil. When I first started the engine after the overhaul I questioned the pressure because it was not as high cold as it was before, same mechanical gauge on tractor. I used the tractor about 11 hours to do the work I needed and as it warmed up the oil pressure was worse. I finished and decided the tractor will not go back in the field until it is fixed. I complained to the dealer and they tried to convince me the lower pressure was from the three valve train rocker shaft supports that they replaced were to improve valve train lubrication. This is wrong because you don't improve lubrication by lowering the pressure. I continued to complain after they changed the oil pressure regulator with no change and then they changed the oil pump with a higher volume pump that they did not know about until I told them about it. The higher volume pump raised the pressure by 2 psi. This engine was sick. They said the engine was fine. They decided to take the tractor to another one of their dealers that was farther from my home to use the PicoScope on it to show the oil pressure was fine because they said mechanical gauges are inaccurate. I disagreed with that statement but decided to see what the electronic gauge shows. I arrived at the other dealer at the time they asked. I was not allowed to see the tractor for 45 minutes. When I was allowed to see the tractor it was running on a pto dyno. They had their PicoScope with the WPS600 transducer installed with a 0-100 psi mechanical gauge T-ed into the oil fitting. I stand and watch the mechanical gauge through their test because I can read it and it reads just like my gauges that I have used. After they run their test and record their readings with the tractor still running now at operating temp and at idle the mechanic walks over to me with his laptop and says see see what it says. I explained to him I don't know and understand his scope and I can't see it in the sun anyhow. He says it reads 28 psi. I point at his mechanical gauge said why does that one read 10 psi. He says no this ones right. I came to the conclusion that this show was to deceive me and not to inform. I had the engine overhauled again somewhere else and aluminum oxide was found in the oil galleries that destroyed the bearings and all close tolerance parts in the engine. The aluminum oxide was from the machine shop cleaning process and was not cleaned from the engine before assembly. The dealer did the final assembly and left around 30 bolts loose and over tightened fuel injection lines damaging the fittings. The second overhaul has all 6 rocker shaft supports installed to improve valve train lubrication that is the latest update that the dealer from the first overhaul failed the be aware of. After the first overhaul oil pressure was 48 psi at high idle and 10 psi at idle at operating temp, not within book specs. After the second overhaul the oil pressure is 65 psi at high idle and 35 psi at idle at operating temp. Well within book spec. The oil pressure relief is set at 65 psi. I believe the dealer added a pressure reading to their test reading and then printed out the results and said this is what your engine oil pressure did. The Pico print outs were considerably higher than what I witnessed on their gauge or on mine. I wanted to see if Paul Danner could run me a test on this equipment if I brought him a WPS600 transducer.
Thank You
OK a lot in your post but my initial reaction is that a reading can't be altered by +18psi by using a vacuum to to lower the datum calibration the most the readings could be biased by in theory is a 1bar (about 14.5 psi) reduction and in practice less than that. Without having used it I would also think the Pico software and hardware won't allow that big an adjustment. If I wanted to rigg an oil pressure test I would use the used car dealers trick and simply dump a couple of tins of STP into the oil.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Hello Andy,
I had the oil analyzed before the test and after. The viscosity did not change. There again when the technician tells me the oil pressure reads 28psi on the Pico, his manual gauge reads a steady 10psi. They used a Pico WPS600 Hydraulic Pressure Transducer. The manual is on the internet. It states that the WPS600 transducer has two scales. One 0-870psi and the other 0-8700psi. It also states that the accuracy is 1% of scale. That would be on the 0-870psi scale of 8.7psi and on the 0-8700psi scale of 87psi. Do you think they lucked out and the transducer reads on the high side of actual pressure on the 0-8700psi scale with an accuracy that could be off as much as 87psi? Could this have been where the extra 18psi came from? I can not tell from their print outs what scale they used.
Thanks,
buzzboy
Hello Paul, Andy, and everyone who has contributed,
Just wanted to let you all know that I have confirmed my suspicion. The Pico WPS600 Hydraulic Pressure Transducer can be manipulated by applying a vacuum to the transducer and then pushing the 60BAR and 600BAR buttons to calibrate. I have purchased my own PicoScope Automotive 6 master kit with WPS600 Transducer. By applying around 18 inches of vacuum to the transducer, with a hand pump, will add around 11 to 14PSI to the Pico reading. I had made a mistake and misheard what the test technician had told me. I understood him to say, with the tractor running beside us, that the pressure was 28PSI on the Pico when the pressure on his manual gauge reads 10PSI. He tries to convince me the Pico is correct because it's electronic. I later discovered the lowest Pico printout they gave me reads 21.8PSI. I believe his response to when I had asked him the pressure was 21.8 not 28. This confirms he added 11.8PSI to achieve 21.8PSI on the Pico reading, 11.8PSI over the 10PSI on his manual gauge and the 10PSI I have read on my many gauges, one which is NIST Certified. With my equipment giving consideration to the static, I can easily add 11 to 14PSI to the Pico reading.
Thanks,
Buzzboy
Hi sorry to hear about the problems you've been having .not nice to think this may of happened as you now have a pico and transducer and just out of interest if you set the transducer at a higher setting and used one of the attenuators this would alter the result ,the attenuators bring down the signal to the pico so hence you would need a higher scale or it would reed lower .on your problem you can't test the tractor as its been altered but ultimately the real question is how accurate or inaccurate is your manual gauge ?.?...assuming you still have it ,,as a good manual gauge at that pressure should be accurate within a few psi .test this by rigging your gauge up with your transducer apply your 28psi and see what it shows
Hello ChrisG,
I have one pressure gauge with a written certification paper that is traceable to NIST. This is a government agency, the National Institute of Standards and Technology. <nist.gov>. It is a 0 to 100psi gauge. This gauge's dimensions are 5 1/16" round X 2 1/16" thick. It has an increment mark every one pound. I ordered this gauge from McMaster-Karr, <McMaster.com>. The test starts, does the gauge read 0 at 0psi. Then they increase pressure to 20, 50 and 100psi and record what the gauge reads. Then they decrease pressure from 100 to 50, 20, then 0psi, then record the gauge readings. The recorded readings of the test for my gauge shows that 2 of the test values are off .25psi or one quarter of a pound per square inch to the rest of the test values reading perfect. I just want to let everyone know the Pico test results can be manipulated. The Pico still fluctuates 1 to 3 psi from static with no application of pressure. Yes you can read the average, but that is still the average of the fluctuation. Pico makes great diagnostic equipment, but in the hands of a irresponsible individual can be used to try to deceive.
FYI Thanks,
Buzzboy
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