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04-08-2008, 08:25 AM
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#29
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Senior Member
Workhorse Chassis Owner
Join Date: Nov 2005
Posts: 423
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hwybnd.....
I like the following:
TM-747X Four Channel Input - DAS PRICE: $199.00
It is expensive and there are some cheaper ones on the websites you provided. Unless it is a 4 channel model there have to be some type of switch to monitor multiple probes.
I also wonder what the maximum length of probe cable these devices will support and the accuracy for long cable runs? Have you found any info regarding that?
Your approach is a good one though for those who don't want to build their own.
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04-08-2008, 09:18 AM
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#30
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Senior Member
Workhorse Chassis Owner
Join Date: May 2004
Posts: 114
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Streamerman: I am looking at the same 4-channel instrument you are. It lacks an alarm feature but according to the detailed description it has a logging feature that can store 16,000 data points.
Here is another one that I like. It has only two channels but has maximum value recording and programmable alarms. There is also a three-channel version.
http://www.coleparmer.com/catalog/pr...sp?sku=3748615
The length of the wires is not a problem in the context of RV brake monitoring. You can go 50 feet easily but you have to be careful about joints. The wire should be one piece. You can buy bulk Type K thermocouple wire and connectors and make your own probes.
__________________
2004 Sea Breeze 8341 WH
Costa Mesa, CA
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04-08-2008, 01:21 PM
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#31
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Senior Member
National RV Owners Club Workhorse Chassis Owner
Join Date: Oct 2004
Location: Scottsdale, AZ
Posts: 1,502
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You may want to consider good shielding on thermocouple runs.
I used an Omega TC instrument to monitor transmission fluids on the cooling lines and picked up rfi noise from the ignition wires.
Shielding totally eliminated problem. I wrapped aluminum foil around each run and grounded at the source end.
__________________
2003 34' Dolphin 5342, W22, UP, UPGBrake, F and R Track Bars, Rear IPD sway bar, Koni FSDs, Safe-T-Plus, Scan Gauge II.. 2004 Jeep Liberty, Blue-Ox Adventa..
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04-08-2008, 06:16 PM
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#32
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Senior Member
Workhorse Chassis Owner
Join Date: Nov 2005
Posts: 423
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M&EM... That's is a good point. I originally planned to use coax but it was proving to be too bulky. I was leaning toward speaker wire. Might re-think the shielded brand.
Thanks for the input,
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04-08-2008, 08:16 PM
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#33
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Senior Member
Workhorse Chassis Owner
Join Date: May 2004
Posts: 114
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Streamerman: Coax or speaker wire won't work. It has to be Type K thermocouple wire or thermocouple extension wire. You can run that inside a shield braid if necessary.
__________________
2004 Sea Breeze 8341 WH
Costa Mesa, CA
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04-09-2008, 03:35 AM
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#34
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Senior Member
Workhorse Chassis Owner
Join Date: Nov 2005
Posts: 423
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Interesting, I tested my signal with 30ft of regular TV coax and there was no loss in voltage level at my controller. It still activated the light and relay at the preset millivolt level.
I'll be doing more testing though.
Thanks,
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04-09-2008, 06:31 AM
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#35
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Senior Member
Workhorse Chassis Owner
Join Date: Oct 2005
Location: UK
Posts: 151
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__________________
04 Brave 30 W20 8.1
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04-09-2008, 09:55 AM
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#36
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Senior Member
Workhorse Chassis Owner
Join Date: May 2004
Posts: 114
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Quote:
Originally posted by Streamerman:
Interesting, I tested my signal with 30ft of regular TV coax and there was no loss in voltage level at my controller. It still activated the light and relay at the preset millivolt level.
I'll be doing more testing though.
Thanks,
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It is not a voltage drop problem. All thermocouples use exotic metal leads and the meters are calibrated for the specific EMFs associated with the junction of those specific metals. Introducing other metals like copper into the circuit causes errors.
__________________
2004 Sea Breeze 8341 WH
Costa Mesa, CA
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04-09-2008, 12:00 PM
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#37
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Senior Member
Workhorse Chassis Owner
Join Date: Nov 2005
Posts: 423
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hwybnb...
Yes I can see where that could be a problem with the manufactured meters. The reason this is not a problem for my home grown controller is that I'm tuning the circuit for the voltage output of the thermocouple.
I went over to the coach today and worked on where to locate the thermocouples and it looks like on the front I will use one of the 5/16-18 tapped holes in the axle housing plate. I will probably use a 1/4 inch adel clamp without the rubber. There is limited depth for this hole to clear the rotor. I purchased stainless 3/4 inch allen head bolts for them.
For the back it looks like will have to fashion some type of bracket and bolt it to the brake line support bolt. This will allow the TC to be positioned in the vent hole behind the rotor.
We'll see how all this works out when I can get to the actual mounting of them.
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04-09-2008, 12:04 PM
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#38
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Senior Member
Workhorse Chassis Owner
Join Date: May 2004
Posts: 114
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I have decided to go with this 4-channel monitor:
http://www.professionalequipment.com/thermometer-with-t...k-type-thermocouple/
It does not have the data logging capability of the $200 model but it stores the maximum value for each channel. After buying some thermocouple wire and a few other goodies I think I can have a 4-Channel system for under $200. I will post more when I get it done.
__________________
2004 Sea Breeze 8341 WH
Costa Mesa, CA
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04-09-2008, 01:11 PM
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#39
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Senior Member
Workhorse Chassis Owner
Join Date: Nov 2005
Posts: 423
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hwybnb....
I look forward to hearing your progress.
Good Luck!
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04-11-2008, 11:40 AM
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#41
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Senior Member
Winnebago Owners Club Workhorse Chassis Owner
Join Date: Jul 2002
Location: Camarillo, CA ---Back in the house after 7 yrs fulltiming
Posts: 1,652
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Hey Steamerman, this is a quite a "high visability" project your got going here. It's like having a real-time peer design review by your irv2 members.
One issue I was thinking you may have is thermal drift as the long cable runs to the rear get hot from the engine & exhaust heat. As the ambient temp goes up while driving/stopping may cause false alarms or a drift in the other direction so it won't alarm at the set point. Not sure about this but just early warning regarding a potential headache.
Also, when using Photobucket, under each photo you upload, is a "IMG Code" that you can use to display the image right in your posting. Rather than copy/paste the link like you did, just copy paste the IMG code. You can go back and edit that posting to make the change.
Best of luck,
__________________
Bill & dear wife Helen
Last of the Chieftains, 2004 39T, W22, UP tune, Banks, Koni's, Safe-T-Plus, SMI brake
2017 Lincoln MKZ Hybrid towed 4-down or my 2008 Jeep Wrangler JK
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04-11-2008, 06:20 PM
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#42
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Senior Member
Workhorse Chassis Owner
Join Date: Nov 2005
Posts: 423
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Thanks for the info Duner, I saw that img but wasn't sure that was what I wanted.
As for the drift. I have not tested this on the coach yet but, the only sensitivity I have seen so far is the TC itself and that is only within 1/2 inch of the tip. The TC millivolt output doesn't seem to be affected by the length of wire. I will have to see if there is any loss or induction caused by the motor once it's attached to the coach. The controller is designed to react to a preset voltage comparison and the TC is the only thing generating voltage within the wire. (I hope)
I think the soaking temperature could be a problem when stopped. From what I have read about the problem though, it seems the temperature would be high when under way and that is what I'll be monitoring for. As long as they cool down, I'm ok with that.
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