User Manual
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4.6 Constant Resistance (CR) Mode
In this mode, the electronic load approximates a resistor. The current draw is varied by the load according to the input
voltage. The performance of this mode is not as fast as in CC or CV mode. This is because it is a sampled system and
response to changing input takes a nite amount of time.
4.6.1 Congure CR Parameters
There are several parameters that should be set up prior to operating in CR mode. Press
so that it lights up, then press )and to access Setup for CR mode. The setup menu will be shown:
The setup parameters are: Range, High (Voltage limit), and Low (Voltage limit). Use the (arrow keys) key to select each
parameter, and use the numeric keypad to change the value. Press (enter) to conrm the change.
Range This value will also act as a limit the allowed resistance setting value.
High This parameter sets the upper voltage limit for the automatic test mode. If the voltage exceeds
this upper limit during the test, the test will fail.
High This parameter sets the lower voltage limit for the automatic test mode. If the voltage exceeds
this lower limit during the test, the test will fail.
4.7 CR-LED Test Function
The Constant Resistance LED mode roughly simulates a diode characteristic. There are 2 main parameters that are set
to accomplish this, the overall resistance and diode threshold voltage (Vd). At input voltages above the threshold (Vd),
the resistance of the load decreases. For example, set the Vd to 1.6 V, R to 0.1 and connect a current limited power
supply. Set the power supply voltage limit to 5 V, and the current limit to 300 mA. When the input is enabled, the
voltage at the input will be approximately 1.6 V, and the current will be 300 mA. This is equivalent to a resistance of 16
Ohms, much larger than the set value of 0.1 Ohms. See Table 4.1.
Like in CR mode, a resistance value is also set. This value sets the slope of the diode characteristic. A 3 V VD, 0.1
Ohms, and 1.38 A results in 3𝑉 + 0.1Ω ∗ 1.38𝐴 = 3.18𝑉.
Voltage Current Equivalent Load Resistance
1.00 0 innite
1.58 15mA 105 Ohms
1.62 0.215 A 7.5 Ohms
1.63 0.3 5.4 Ohms
1.69 1 A (limit changed) 1.7 Ohms
Table 4.1 CR Mode example
4.7.1 Setup
Enable CR-LED mode via + . Use the arrow keys to move the ashing value “ON”. Press to conrm
and move on. The next screen shows the VD value. Enter the desired threshold voltage and press . CR LED mode
is now setup.
Note: As in CR mode, the control system speed can make loading switching power supplies problematic.