Unit N.
2: Digital/Analog converter
Purposes:             Verify the operation of a digital to analog converter
Requisites:           Acquisition of Lessons 1 and 2 of Module DL 3155M21R (Theoretical
                      guide)
Instruments:          Digital multimeter
                      Cable set
                                Digital/Analog converter
Electrical Diagrams
                                           Fig. 2.1
Components List
16 resistances 330-1/4W-5%
8 green LED diodes 3mm
8 red LED diodes 3mm
N1 = AD570
8 slide switches SLG1201
Calculation data
Output voltage = decimal value · quantum
Quantum = FRS/2n , i.e. 10V/28
Topographical diagram
                                     Fig. 2.2
Obtained Results (FSR=2.56 V)
                    Digital Inputs              Analog Output
           Binary                                  Uo [V]
                  Hexadecimal Decimal
         76543210                     Calculated Value Measured value
         00000000     00         0            0             0.01
         00000001     01         1          0.01            0.02
         00000010     02         2          0.02            0.03
            ....
         00001111     0F        15          0.15            0.16
         00010000     10        16          0.16            0.17
             ....
          01111111             7F           127           1.27                1.29
          10000000             80           128           1.28                1.29
             ....
          11000000             C0           192           1.92                1.93
             ....
          11111111             FF           255           2.55                2.57
          00000011             03             3           0.03                0.04
          00000100             04             4           0.04                0.05
          00000101             05             5           0.05                0.06
          00010001             11            17           0.17                0.18
          00010010             12            18           0.18                0.18
          00010011             13            19           0.19                0.19
                                             Tab. 2.1
EXPERIMENTATION
 insert the Module DL 3155M21R in the console and set the main switch to ON;
 carry out the connections like in Fig.2.2;
 connect the digital voltmeter 1 between jacks Uo and GND (Fig.2.2);
 set all the deviators to “L”;
 calculate for all the values of the input bits shown in Tab.2.1 the output voltage and write the
 values in the same table;
 measure the eventual offset voltage present in output; this voltage is a mistake that is common
 to all the following measurements, so it will have to be subtracted to the measured values, to
 obtain the true value of the conversion;
 set the deviators “H” according to the digital codes written in Tab.2.1;
 write the values read on the multimeter in Tab.2.1;
 compare the calculated values with the measured ones;
 comment the results.
        QUESTIONS
      An 8 bit D/A converter, with a full scale value if 10V, presents a resolution of:
                                                                                          Answer:
             1.25 %
             125 %
             3.9 %
             0.03 %
      The greatest is the bit number of a converter the lower is its resolution:
             True
                                                                                      Answer:
             False
      At a D/A converter, with fs value = 10V, the binary number 10000000 is applied in input,
      which is the value of the output voltage?
             5V
             4V
                                                                                      Answer:
             3.5 V
             3V
         TROUBLESHOOTING
Push the INSERT button to insert the fault in the circuit.
Repeat the operations in the EXPERIMENTATION section to find the fault inserted in the
circuit.
       Which is the fault ?
             DB3 output interrupted
             Not supplied converter
                                                                                      Answer:
             Converter output interrupted
             B2 input interrupted
  Remove all the connections.