University of Massachusetts
Department of Electrical & Computer Engineering
ECE 210 Circuits and Electronics I
Fall 2020
Project 1: DC Measurements of a Photovoltaic Device
Purpose:
1) Become familiar with current, voltage, and power in a practical device.
2) Become familiar with the use of Voltmeter and Ammeter measurements
Preparations: Prelab Homework 1 must be completed prior to performing this lab.
Deliverable: In order to get credit for the lab, the data sheets in the appendix and the
measurements demonstrated to the instructor.
Introduction
The device you will be measuring (see Figure 1) in this lab is a photovoltaic (PV)
device which is a smaller version of the PV panels you commonly see on buildings and in
solar farms all across the state. Each of the two devices in the figure consists of many
smaller PV cells connected in series and shunt. Each
two terminal device converts light to electrical power
for a “load” which could be something like an LED, a
battery charger, a radio, etc. In this lab the load will
be a resistor. The amount of power transferred to the
load resistor depends on the number of PV cells in the
Figure 1. Two PV devices.
device, the amount of light incident on them, and the
load resistance. For each PV device, there is an optimum resistance that will extract the
most power possible1. You will find this optimum resistance as part of your lab.
Put another way, the optimum load creates the set of terminal voltage and current that extracts the most
power from a PV panel. The optimum changes with the incident sunlight and temperature. Something
called a “maximum power point tracker” (MPPT) is a device used in a solar installation to adjust the load
so that the most power is always extracted from a panel.
1
1
Procedure
Each kit has two PV devices. Place them adjacent to each other in the sun or beneath a
lamp. Use masking tape to keep them stable (as in Figure 1.) To get good results for this
lab, you need a constant light source. A cloudy or partly cloudy day will make it
difficult to get good results. A lamp would then be a better source even though it will
supply less power than the sun.
1) Measure the open circuit voltage of one device. Connect the multimeter to the device,
set the multimeter to measure voltage(See Appendix I. Set the meter to the 4V scale at
about 1:00 o’clock on the front face dial). When the multimeter is set to voltage
measurement, it draws very little current from the thing it is measuring. In other words it
presents a very high resistance (10Mohms) to the circuit under test. To the PV device it
looks like an open circuit. Measure and record the open circuit voltage. Check what
happens when you block the light with your hand.
2) Measure the short circuit current. Connect the multimeter to the device, set the
multimeter to measure current (See Appendix I. Change the knob to the 400uA scale at
about 10:00 o’clock). When the multimeter is set to current measurement, it presents a
very low resistance (10ohms) to the circuit under test. It almost looks like a short circuit.
Measure and record the short circuit current. Check what happens when you block the
light with your hand.
3) Measure the I-V characteristic of the PV device. Use the ADALM as a voltage source
and the multimeter as an ammeter, connect them as shown in Figure 2. See Appendix II
for instructions for using the ADALM voltage source. Start out with the voltage set to
zero. You should see the same current as in (2) above. It will be negative. Then increase
the voltage in 0.1 volt increments and record the currents measured. Stop when the
current reaches zero. Plot the current versus voltage on the graph paper in the Appendix.
2
Calculate the power sourced by the PV cell for each voltage you measured. Plot the
power versus voltage on the same graph. Record the maximum power, the corresponding
voltage and current. What resistance will extract the most power from the cell?
I
PV
device
+
ADALM2000
voltage source
V
_
multimeter
(ammeter)
Figure 2. (a) PV device with voltage source and ammeter
(b) a realization (Fluke multimeter)
4) Connect two PV devices in series as shown in Figure 3. As best as possible illuminate
both devices as you did in the above steps. Measure the I-V characteristic of the series
combined cells a you did in (3). Plot the current versus voltage on the graph paper in the
Appendix. Calculate the power sourced by the PV cell for each voltage you measured.
Plot the power versus voltage. Record the maximum power, the corresponding voltage
and current. How does the maximum power compare to (3) above? What resistance will
extract the most power from the cell?
I
PV 1
+
ADALM2000
voltage source
V
PV 2
_
multimeter
(ammeter)
Figure 3. PV devices connected in series with voltage source and ammeter
3
5) Connect two PV devices in shunt as shown in Figure 4. As best as possible illuminate
both devices as you did in the above step. Make RL in the figure zero and measure the
current with the ammeter. How does it compare with the short circuit current measured
in step 3? The resistance that extracts the most power from the shunt combination is
about ½ of the value you found in step 3. Find a resistor close to this value from your
parts box and connect it as RL in Figure 4. Measure the current through the load with the
ammeter. Calculate the power dissipated in the load. Compare it to the maximum power
in steps 3 and steps 4.
I
PV 1
PV 2
IL
+
RL
V
_
multimeter
(ammeter)
Figure 4. PV devices connected in shunt with multimeter set for current measurement
4
Appendix I Multimeter
The front face of a multimeter is shown below. This particular multimeter measures DC
voltage, AC Voltage, resistance, capacitance AC current and DC current.
Figure A1. Front face of the M-1750 Multimeter.
Note that the leads plug in at the bottom. The black
lead plugs into common. The red lead plugs into
VWmA
5
Appendix II DC power supply
Figure A2 shows the user interface for supplying voltage to your circuit. The
supply provides two voltage sources, one supplies positive voltage (the V+ and ground
(a)
(c)
(b)
(d)
Figure A2. Scopy user interface for the DC power supply
leads) and the other supplies negative voltage (the V- and ground leads.) This appendix
describes setting the plus supply that you need for this lab. You can find more detailed
instructions at
https://wiki.analog.com/university/tools/m2k/scopy
https://wiki.analog.com/university/tools/m2k/scopy/power-supply
You can set the voltage level by typing in the voltage you want at (a). The little arrow (b)
is used to set the scale to mV or V. The figure shows a setting of 650 mV. You can
increase or decrease the level using the +/-. When the orange dot (c) is clicked on, the +/changes the level by 0.1 volt. When the orange dot is clicked off, the +/- changes the
level by 1.0 volt. The “VDC Set” shows the voltage you set. That voltage is not applied
to the leads until you click on (d) “enable.” “VDC Measure” shows the voltage measured
at the leads after “enable” is clicked..
6
Appendix III
Illumination Conditions
Illumination method:
Sunlight? Time of day?
Lamp? How far from lamp?
1) Measured open circuit voltage one PV cell:
fly
lamp
right
①
__________________Volts
0.98
2) Measured short circuit current one PV cell ___________________
mA
-
3) Measure I versus V for one PV cell
V (volts) I (mA)
O
-
I
0.2
0.3
0.4
0.5
0.6
oil
0.8
P(mW)
V (volts) I (mA)
-0.88 0.088
0.870,174
-
-
0.86
-0.83
-
-
0.258
0.332
0.76
0,38
0.62
0.372
-0,374
0.262
0.006 6.048
7
P(mW)
under
lamp
3) continued
40
:
5
4
32
I
0.8
0.6
0.4
0.2
Ego
-
.
.
V
t
§I
EE
.-ii-
.
O ul
0.2
0.3 0.4 0.5
0.6 0.7%8
V V ( volts )
0.1
0.2
on
0
to
,
Of
•
*
•
•
a
I
5
:
40
Plot I versus V for single cell.
Plot delivered power versus V for single cell
0.65852
Find optimum resistance: _____________________
8
i. Iv
4) Measured open circuit voltage for two series connected cells:____________________
1. 63kV
Two times single cell open circuit voltage measured in (3) :__________________
4%
% difference:________________
Measure I versus V for two PV cells in series
V (volts) I (mA)
P(mW)
V (volts) I (mA)
P(mW)
I
-0.757
0.757
0.156
I. I
-0.756
0,832
0.234
1.2
-0.745
0.814
0,309
1.3
-0.711
0.924
0.5 -0.77
0.385
1.4 -0.633
0.886
0.6
-0.766
0.46
1.5
-0.5
0.75
0,7
-0.765
0.536
1,6
-0.307
0.49
0.8
-0.76
0.608
1.7
Org
-01758
0.682
1.8
-0.79
0.079
0.2
-0,78
0.3
-0.78
0.4
-0.773
0
.
I
'
-
0.045
0.29
0.077
0.522
1. 8281
Optimum resistance for series connected pair:______________________
0.924mW
Measured optimum power series connected pair:________________
Two times single cell optimum power measured from (3) :__________________
0.76mW
% difference:________________
21.58%
1.615mA
5) Short circuit current for shunt connected pair:______________________
-
1.98mA
2 times short circuit current from step (2):______________________
-
% difference:________________
22.6%
9
0.37bar
Optimum resistance RLopt for shunt connected pair:______________________
*
Resistance from parts box approximating RLopt::_________________
1.33mA
Measured optimum current using ammeter:_________________
-
0.665mW
Calculated power from measured current and RL used in circuit:_________________
2 times optimum power from part (3):______________________
0.76mV
1429%
% difference:________________
0.665mW
Measured optimum power shunt connected pair:________________
0.76mW
Two times single cell optimum power measured from (3) :__________________
% difference:________________
14.29%
Instructor Sign-off:_______________
0.1
1.55
A. 2
1.54
0,3
0.6
0.5
1,516
1.46
0.584
1.33
0.6652
o.by
on
o
-8
,
Og
0.654
0.707
OI
6.
41
10