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Sitrans Probe LU Problems

Created by: hhpp at: 7/11/2011 5:08 PM (13 Replies)

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7/11/2011 5:08 PM	Rate (0)
hhpp Posts: 20 Rating: (0)	Hello my name is Héctor I have a few problems with some instruments. I ha many sitrans probe LU already installed and working but some of them do not work fine. The first one: sitras probe LU 12 meters range is installed in a 10 meters tank(height) totally closed tank (water). It has been like 3 months since it was installed, andI havethis problem since then. The instrument shows 100 % of level when itis absolutely empty, I check the empty parameter, the span parameter,but i did not work. I di also the P837, 838 to prevent false echoes but nothig. Every morning I go the stank check the same problem, I do a reset andagain the p837, 838, turn off the instrument and after five minutes turn on. It work fine during the day, but the next day the same problem. Ido notknow what is going on, may be the low temperature duroing the night (- 10celcius degrees ann somedays-20 ), but i am not sure. Do you think thatthis problem could be solved? Thanks hp.
hhpp Posts: 20 Rating: (0)
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7/11/2011 6:33 PM	Rate (0)
Toppie Posts: 74 Rating: (3)	Hello Héctor Can you advise how the Probe LU is mounted, where on the tank top, the shape and dimensions of the tankand some of the parameters from P001 to P007, P800 and P801.Since you'll be at the top of the tank you may as wellget the P805 and P806 values too. My first suspicion would be that it is too tightly installed and when it gets very cold at night the damping materials in the transducer portion are not as resilient and we are getting a bit of ringing near the top of the tank. If mounted close to the wall, you may be gettins some sidewall echoes. If a prabolic bottom tank and you haveinsufficient range extension (P801)and fail high, you may be triggering on LOE (loss of echo) High P806 with low P805 tells me a multiple echo or ringingsituation. Low P806 and low P805 tell me athe echo is not received and a possible LOE. When performing the AFES (P837 / 838) you will need to make sure that the P838 distance you set is not in the range of the material. Sounds obvious but needs a mention. Regards [ \|:) Toppie
Toppie Posts: 74 Rating: (3)
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7/12/2011 9:50 PM	Rate (0)
hhpp Posts: 20 Rating: (0)	Hello Toppie and tanks again: attached is a drawing where I show the intrument location on the top. All are in milimeters, what do you think? hp. Attachment tank.pdf (449 Downloads)
hhpp Posts: 20 Rating: (0)
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7/12/2011 11:05 PM	Rate (1)
SonicRanger Posts: 151 Rating: (8)	Hi hhpp, The Probe LU works with both "long shots", for measuring range >1m and "short shots", for measuring range < 1m. Combined with the low temperature, maybe you have false echoes in the short shot window. Try to maximize the blanking distance (P800) to the value of P006 minus P007. When you find a 100% reading at an empty tank, what is the value of P805 (xx:yy)? Does it reach the treshold in the short shot, i.e. is the left value (xx) 10 ? And try to mount the probes not more than hand-tight on the nozzles / flanges, this can minimize the amount of ringing (near sensor disturbances. Does the sensor have a free "sight' in the tank, or is it mounted in a standpipe? Best Regards, SonicRanger
SonicRanger Posts: 151 Rating: (8)
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7/13/2011 5:02 PM	Rate (0)
Toppie Posts: 74 Rating: (3)	Hi Hector I think Sonic Ranger has covered it very well. You may be too tightly mountedand you may be able to increase the blanking range a little to hide any signal that may be casuing a false near echo. Please do check the tighness before extending the balnking as this may be the cause of the false near echo. I think your mounting in the tank is good with the normal 10 down and 1 over being satisfied. Best regards Toppie [ \|:)
Toppie Posts: 74 Rating: (3)
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7/14/2011 4:10 PM	Rate (0)
hhpp Posts: 20 Rating: (0)	Hello and thanks everybody. Here I have the parameteres when the tank is empty and reading 101%: P001=1 P002=1 P003=1 P005=1 P006=9.95 m P007=9.25 m P800= 0.25 m P801=20% P804=10:5 P805=0:6 P806=50 P837=1 P838=9.5 m It was installed on a standpipe 2" NPT (threaded), as far as i can see the tightness was tightly. Meanwhile (fis the standpipe)i am doing a test, I am installing the instrument on the open square that I showed in the drawing next to the "ex" instrument location". I am not surebut fo fari am getting same problems, let´s see during the day and night. I increase the blankingdistance to 0.7 m. what do you think.?
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7/14/2011 5:54 PM	Rate (1)
Toppie Posts: 74 Rating: (3)	Hector You have lots of signal P806 is 50dB but you have too many echoes. This is shown by the very poor Confodence P805. A 2" standpipe is pretty small, too small for a 10 m shot. Your multiple echoes may be coming from this. Why the standpipe? Is there splashing or foam? It should work better without the standpipe but make sure it is not mountned tightly, only hand tight because the above symptoms can be casued by "ringing" which is an accoustic coupling to the tank. If the weather gets extremely cold it's a good idea to extend the balnking P800 to at lease 300mm but make sure the level will not come into the blanking zone. Toppie [ \|:)
Toppie Posts: 74 Rating: (3)
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7/15/2011 9:37 PM	Rate (0)
SonicRanger Posts: 151 Rating: (8)	Hi hhpp, P838 is chosen rather high, maybe the filter set with auto false echo surpression interferes with the signal of the tank bottom. I would recommend to set it at a lower value (e.g. 8,5 m), and relearn the tank curve. 2 more tips: - switch the auto false echo surpression off, and read the confidence value again; - try different algorithms, and read the confidence value again. Regards, SonicRanger.
SonicRanger Posts: 151 Rating: (8)
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7/18/2011 2:17 PM	Rate (0)
Toppie Posts: 74 Rating: (3)	Good catch on P838, SonicRanger. I suspect his AFES is hinding a whole bunch of ringing from the narrow standpipe and possibly tightness/cold weather. Cheers
Toppie Posts: 74 Rating: (3)
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7/18/2011 9:19 PM	Rate (0)
SonicRanger Posts: 151 Rating: (8)	Hi Toppie, about the cold weather: do you know how the learned auto-false echo surpression deals with changes in temperature? What happens if the curve is learned at 30 deg C, and the temperature decreases to -10 C for example? I guess this can be a tricky situation... Best Regards, SonicRanger.
SonicRanger Posts: 151 Rating: (8)
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