Sea-Bird Electronics SBE 38 Bedienungsanleitung PDF herunterladen (Seite 18)

Manual revision 006 Section 2: Description of SBE 19plus V2 SBE 19plus V2

Supplying Enough Power to SBE 19plus V2

Another consideration in determining maximum cable length is supplying

enough power at the power source so that sufficient voltage is available, after

IR loss in the cable (from the turn-on transient, two-way resistance), to

power the 19plus V2. The table summarizes the maximum 2-way resistance

for various input supplies and pump configurations:

Power Supply Input

and Pump Configuration

limit

= Maximum 2-way

Resistance (ohms)

3 amps at 9V input, SBE 5M pump

(cannot use SBE 5T or 5P pump with 9V input)

0.5 amps at 12V input, SBE 5M pump

3.0 amps at 12V input, SBE 5T or 5P pump

0.5 amps at 19V input, SBE 5M pump

1.5 amps at 19V input, SBE 5T or 5P pump

Calculate maximum cable length as:

Maximum cable length = R

limit

/ 2 * wire resistance per foot

Example 1 – For 20 gauge wire, what is maximum distance to transmit power to 19plus V2 if using 12 volt power source

with SBE 5T pump?

Maximum cable length = R

limit

/ 2 * wire resistance per foot = 2 ohms / 2 * 0.0107 ohms/foot = 93 ft = 28 meters

Note that 28 meters < 173 meters and 474 meters (maximum distance if transmitting real-time data in examples above),

so IR drop in power is controlling factor for this example. Using a higher voltage power supply or a different wire gauge

would increase allowable cable length.

Example 2 – Same as above, but there are 4 instruments powered from same power supply.

Maximum cable length = R

limit

/ 2 * wire resistance per foot * 4 instruments

= 2 ohms / 2 * 0.0107 ohms/foot * 4 = 23 ft = 7 meters (to 19plus V2 furthest from power source)

Moored Mode Examples – use 65 mA communication current, regardless of 19plus V2 configuration

Example 1 – For 20 gauge wire, what is maximum distance to transmit power to 19plus V2 if transmitting real-time data?

For 65 milliamp communications current, R

limit

= V

limit

/ I = 1 volt / 0.065 amps = 15.4 ohms

For 20 gauge wire, resistance is 0.0107 ohms/foot.

Maximum cable length = 15.4 ohms / 0.0107 ohms/foot = 1439 feet = 439 meters

Example 2 – Same as above, but there are 4 instruments powered from the same power supply.

For 65 milliamp communications current, R

limit

= V

limit

/ I = 1 volt / (0.065 amps * 4 instruments) = 3.8 ohms

Maximum cable length = 3.8 ohms / 0.0107 ohms/foot = 355 feet = 108 meters (to 19plus V2 furthest from power source).

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