How does the Analog to Digital Conversion work?
An Analog-to-digital converter(ADC) converts a analog signal, like sound from a microphone or light entering a camera, into a digital signal. An ADC may also provide an isolated measurement such as an electronic device that converts an input analog voltage or current to a digital number representing the magnitude of the voltage or current.
Examples include:
Music recording
In the 2000s era music reproduction technology and digital audio workstation-based sound recording used analog to digital converters. People i often i produce i music i on i computers i using i an analog i recording i and i therefore i need i analog-to-digital i converters i to i create i the i pulsecode i modulation(PCM)data i streams i that i go i onto i compact i discs i and i digital i music i files.
Scientific instruments
Cameras often use analog-to-digital converters in the digitizing of pixels. Some radar systems commonly use analog-to-digital converters to convert signal strength to digital values for subsequent signal processing.
Digital signal processing
ADCs i are i required i toiprocess, i store, i or i transport i virtually i any i analog i signal i in i digital i form. TV i tuner i cards, i for i example, i use i fiast i video i analog-to-digital i converters.

How does the Digital to Analog Conversion work?
An ADC inputs an analog electrical signal such as voltage or current and outputs a binary number. It is much easier to convert a digital signal into an analog signal than it is to do the reverse. There are several DAC architectures; the suitability of a DAC for a particular application is determined by figures of merit including: resolution, maximum sampling frequency and others. Digital-to-analog conversion can degrade a signal, so a DAC should be specified that has insignificant errors in terms of the application.
Audio
Most modern audio signals are stored in digital form (for example MP3s and CDs) and, in order to be heard through speakers, they must be converted into an analog signal. DACs are therefore found in CD players, digital music players, and PC sound cards.
Video
Video signals from a digital source, such as a computer, must be converted to analog form if they are to be displayed on an analog monitor.
Mechanical
A one-bit mechanical actuator assumes two positions: one when on, another when off.
Where are these systems used at sea?
Some examples analog to digital conversion on a ship are:
 Temperature sensors
 Radar systems
 Microphone
 Steering
 Fire detection
Some examples digital to analog conversion on a ship are:
 Valves
 Speakers
 Computer monitors
 LED lights
 Electric motor speed

How are they calibrated?
An example I will use is from a tank gauge.
The tank gauge consists of a transducer, an amplifier and a cable. The sensor is protected by an isolation diaphragm. Pressure changes on the front of the diaphragm and this causes a resistance change in the Wheatstone bridge of the transducer. The change in the Wheatstone bridge will be transmitted to the amplifier as a change in the electrical signal.
How to calibrate with pressure
1.
Set the calibrator output selector switch/pump to pressure mode and connect it to the MAS
2600 transducer by a Test Cup. Test cup type G022S100 are used for calibrator type DPI610 and DPI603. Test cup type G022S103 are used for calibrator type DPI802P CAL KIT.
2.
Connect the mA output signal from the amplifier to the calibrator by use of connector type
G022S101.
3.
Check that the range select switch is correctly set.
The select switch ranges are indicated on the lid inside the amplifier box.
The transmitter output signal can be adjusted to 20 mA within the selected sub-range.
4.
In conditions of no pressure (atmospheric pressure) the output signal should be adjusted to
4.00 mA on the ZERO potentiometer.
5.
Increase the pressure to maximum and adjust the output signal to 20.00 Ma on the SPAN potentiometer.
6.
Remove the pressure and check the zero point.
7.
Check the linearity at 0-25-50-75 and 100% of the measuring range.
8.
If Necessary, repeat the steps 3 to 6.
Calibrating with Vacuum
The MAS 2600 transmitter can also be calibrated by use of vacuum. This can be useful if the transducer is internally mounted. However, prior to the calibration check that no liquid are above the Diaphragm of the transducer as this will cause a wrong calibration.
1.
Set the calibrator output switch/pump to vacuum mode and connect the vacuum test hose to the MAS 2600 Transmitter through the breather tube of the transducer cable located in the amplifier.
2.
Connect the mA output signal from the amplifier to the calibrator by use of connector type
G022S101.
3.
Check that the tank is empty.
4.
Check that the range select switch is correctly set.
5.
In condition of no pressure/vacuum the output signal should be adjusted to 4.00 mA on the
ZERO potentiometer.
6.
Increase the vacuum equal to the maximum height of the fluid (water gauge) and adjust the output signal to 20.00 mA on the SPAN potentiometer.
7.
Remove the vacuum and check the zero point.
8.
Check the linearity at 0-25-50-75 and 100% of the measuring range.
9.
If necessary, repeat steps 4 to 7.
Aligning the Level Transducer:

The range is predetermined and must be selected on the amplifier by flicking the number specified switch up.

Set the calibrator to pressure mode and connect it to the transducer by use of the test cup

Connect the output signal coming from the amplifier to the calibrator

Release the pressure from the pump, the pressure value should be at 0bar.

Adjust the output signal from the amplifier to 4mA using ZERO on the potentiometer.

Increase the pressure to the max value given.

When pressure is at its max, adjust the output to 20mA using the SPAN on the potentiometer.

Check values from zero to max and cross reference with the predetermined values.

What is the danger if one of these systems goes wrong?
If there is a fault on something as serious as the fire detection systems on board it would be a huge problem. The detector head gathers a reading of smoke or heat (digital) in its area and this comes back as a reading. If this was in fault you would get an incorrect indication of the environment in which it is. This would allow a buildup of smoke or even a fire which would go undetected.
Another system I can think of is the overheat sensor on the DG’s. Theses sensors have a set temperature at which the Engine can reach until it trips. Incorrect readings would allowed an engine to overheat to a temperature that may result in damage to equipment and/or fire.