Points North Ltd.

Marine Gyro Compass / Navigational & Communication Systems   Marine Electrical & Electronic Systems

INTRODUCTION

The interface converts NMEA 0183 data from navigation instruments or sensors such as echo sounder & log into a 4 to 20 mA current loop. 4-20 mA is an industrial standard commonly used to drive analogue indicators, data loggers, chart recorders and engine control systems. +/-10 volts and other voltages are also used. The interface can output:

• 4-20 mA or
• +/-10 volts or.
• +/-5v or 0 to+5 volts 

The list of data handled so far is shown below. If your requirement is not here let us know and we can program the interface to suit you.

The interface is a development based on the previous model, made necessary because the 4-20 mA chips used became unobtainable. It uses the AD420 high precision 16 bit DAC chip.

SPECIFICATION

INPUT:          NMEA 0183, RS422 or RS232 via opto isolated channel.

4-20 mA OUTPUT: Max voltage 10 volts so 500 ohms is the highest value load.

Accuracy is typically better than 1%. 

The current goes to zero if there is no input data.

Isolated from power, data and ground.

VOLTAGE OUTPUT:  +/- 10 volts for future options. 10K load minimum.

DATA OUTPUT: NMEA 0183 for monitoring & test. Bi-colour status LED.

OPTIONS:        Selected by switch on the PCB.

(Compatible with previous version dual channel interface, the 920-SV outputs the previous version’s channel 1 data, but with the advantage of higher voltage.)

The interface must be fitted with the OPAMP output circuit to give the voltage output.

NO-INPUT:        If there is no data input the output current will fall to less than 1 mA. Receiving equipment should recognise this as being a fault condition.

Option 0.         All valid gyro or magnetic NMEA sentences.

00 0000OUT:     4 -20 mA for 000 to 360 degrees. (Precision is not to a deg.)

Option 1.          IN:       Marimatech Echo Sounder data. (E-Sea sound format.)

00 0001OUT:     4 -20 mA for 0 to 160 metres depth.

Option 2.          IN:        NMEA 0183 rudder angle, $ERRSA,x.x,A,x.x,A cr lf

00 0010            Where the values are in degrees 0 to 359.9

                        OUT:     4 -20 mA for 0 to  360 degrees. (Precision not to 1 deg)

Option 3.          IN:        $ERRPM Revs per minute

00 0011OUT:     Starboard inner 4 -20 mA for –1300 to +1300 RPM

Option 4.          IN:        $ERRPM Revs per minute

00 0100OUT:     Starboard outer 4 -20 mA for –1300 to +1300 RPM

Option 5.          IN:        Ground or water speed NMEA 0183  $--VBW

00 0101OUT:     4 -20 mA for –8.0 to +30.0 knots

Option 6.          IN:        GPS speed over ground  $GPVTG, RMC,  0 to 30 knots.

00 0110OUT:     4 -20 mA for –8.0 to +30.0 knots

Option 7.          IN:        GPS speed over ground,  $GPVTG, RMC, 0 to 30 knots

00 0111OUT:     4 -20 mA for –8.0 to 30.0 knots

Option 8.          IN:        Depth $SDDBT or $SDDPT        

00 1000OUT:     4 -20 mA for  0 to 50 metres. (Over 50 metres = 20 mA,)

Option 9.          IN:        Rudder angle $AGRSA, $APRSA or $IIRSA

00 1001OUT:     4 -20 mA for +/- 45 degrees. 12 mA = Midships

Option 10.        IN:        Rudder angle $AGRSA, $APRSA or $IIRSA

00 1010OUT:     4 -20 mA for +/- 30 degrees. 12 mA = Midships

Option 11.        IN:        $HEHDT heading

00 1011OUT:     +/- 10 volts. –10v= 180deg.  0v=0 deg.  +10v=179.9

Option 12.        IN:        Rudder angle, $AGRSA, $APRSA or $IIRSA

00 1100.            OUT:     +/- 10volts for +/- 40 degrees.

Option 13.        IN:        Water Speed

00 1101.            OUT:     4-20 mA for - 8 to +30 Knots.

Option 14.        IN:        $HEHDT Heading

00 1110.            OUT:     Sine of heading +/- 10 volts peak to peak.

Option 15.        IN:        $HEHDT Heading

00 1111.          OUT:    Cosine of heading +/- 10 volts peak to peak.

Option 16.        IN:        GPS Speed

01 0000.            OUT:  4 - 20mA for 0 to 16 Knots. 

Option 17.        IN:        LOG Speed

01 0001.            OUT:  4 - 20mA for 0 to 16 Knots.

Option 18.        IN:        Echo Sounder

01 0010.            OUT:     4 - 20mA for 0 to 40 metres.

POWER:       9 to 28 volts DC at  less than 200 mA. 

HOUSING:    Duck Egg Green diecast box 222 x 155 x 55 mm for bulkhead mounting.

Fitted with cable glands.

Removable terminal blocks on the PCB.