NASA electromagnetic log questions

[cpedw]

I just completed installation of EML 3, the version of NASA log that provides pulses to my ST60 head. Two questions :

1. Since we're out of the water, is it feasible to calibrate the log's zero using a bucket of seawater? Any idea how deep the water needs to be? It will be easier to ensure no flow in a bucket than when afloat!
2. After installing, the lights work as expected and the ST60 shows about 12 kts with the sensor in the air. Is that consistent with everything working?

TIA
Derek

 

[Andrew_Trayfoot]

I had the NMEA 0183 version for three seasons with no issue.
Wait until you are on the water to calibrate.

 

[Alex_Blackwood]

I had the NMEA 0183 version for three seasons with no issue.
Wait until you are on the water to calibrate. You can damage the transducer

+1 switch it off until you are afloat. Transducer needs a bit of cooling can be damaged if switched on in air.

 

[RogerJolly]

I'm in a similar situation - kit ready to be installed.

Thinking of doing a test rig though first with motorbike battery and spare Raymarine i50 display. Bit of water in the bath and zoom the transducer up and down looking for a readout.

Bit of a comical idea I guess but wanting to avoid the potential hassle of dealing with potential problems afloat (floods while extracting transducer etc.)

Wondering:

* Would it work with non-salty water (can always add salt to the bath if not!)?

* Is the i50 display compatible (documented to be compatible with ST60 but guessing it's the same pulse signal format).

* Will it work using the existing paddle transducer signal cable instead of the supplied-by-NASA cable (coax). (This one more for install on the boat time)?

I'll probably just suck and see.....

 

[Alex_Blackwood]

I'm in a similar situation - kit ready to be installed.

Thinking of doing a test rig though first with motorbike battery and spare Raymarine i50 display. Bit of water in the bath and zoom the transducer up and down looking for a readout.

Bit of a comical idea I guess but wanting to avoid the potential hassle of dealing with potential problems afloat (floods while extracting transducer etc.)

Wondering:

* Would it work with non-salty water (can always add salt to the bath if not!)?

* Is the i50 display compatible (documented to be compatible with ST60 but guessing it's the same pulse signal format).

* Will it work using the existing paddle transducer signal cable instead of the supplied-by-NASA cable (coax). (This one more for install on the boat time)?

I'll probably just suck and see.....

Not worth the hassle on any of the above. Probably won't work properly with existing cable and any readings in the bath will be different from installed. Don't know about the display.

 

[cpedw]

* Will it work using the existing paddle transducer signal cable instead of the supplied-by-NASA cable (coax). (This one more for install on the boat time)?

I'll probably just suck and see.....

IMPORTANT
DO NOT REDUCE OR INCREASE
THE TRANSDUCER CABLE LENGTH.

I don't know why but this is on Page 5 of the manual.

 

[RogerJolly]

IMPORTANT
DO NOT REDUCE OR INCREASE
THE TRANSDUCER CABLE LENGTH.

I don't know why but this is on Page 5 of the manual.

Thanks for warning.

Bad wording on my part - was talking about the cable from interface box to instrument head, rather than interface box to transducer cable.

NASA manuals terrible - comes with the budget price I guess. Raymarine the other way - take you about 5 weeks reading one of their manuals word for word.

 

[Alex_Blackwood]

Thanks for warning.

Bad wording on my part - was talking about the cable from interface box to instrument head, rather than interface box to transducer cable.

NASA manuals terrible - comes with the budget price I guess. Raymarine the other way - take you about 5 weeks reading one of their manuals word for word.

You have two totally different systems using different signals. Use the cable for the system!

 

[cpedw]

+1 switch it off until you are afloat. Transducer needs a bit of cooling can be damaged if switched on in air.

This has been puzzling me. The stated consumption is <1W shared between the transducer and interface. I find it hard to believe that cooling the transducer is an issue.

 

[Alex_Blackwood]

This has been puzzling me. The stated consumption is <1W shared between the transducer and interface. I find it hard to believe that cooling the transducer is an issue.

The transducer puts out an RF pulse and they can overheat if not cooled.

 

[ithet]

Thanks for warning.

Bad wording on my part - was talking about the cable from interface box to instrument head, rather than interface box to transducer cable.

NASA manuals terrible - comes with the budget price I guess. Raymarine the other way - take you about 5 weeks reading one of their manuals word for word.

I would really need to use the original cable from the interface box (mounted below) to the ST60 at the helm. Its a difficult cable run involving moussing through a conduit otherwise. I think it would not be a problem using the original wire as the Nasa unit is simulating the signals to the ST60 which are at quite a high voltage level (0v, 5v) and what the original cable was designed for.

 

[AntarcticPilot]

IMPORTANT
DO NOT REDUCE OR INCREASE
THE TRANSDUCER CABLE LENGTH.

I don't know why but this is on Page 5 of the manual.

And when I enquired (because a longer cable would have been useful, they emphasized that the length of the cable is important.

 

[cpedw]

I would really need to use the original cable from the interface box (mounted below) to the ST60 at the helm. Its a difficult cable run involving moussing through a conduit otherwise. I think it would not be a problem using the original wire as the Nasa unit is simulating the signals to the ST60 which are at quite a high voltage level (0v, 5v) and what the original cable was designed for.

I think you're OK to use the old cable downstream of the interface box. The warning in the manual is about the cable from transducer to interface.