BK Precision 8500B Series - 6.9 LED Test Mode and Configuration

Operation Modes 62
6.9 LED Test Mode
The Constant Resistance LED mode approximates a diode characteristic by conguring two main parameters:
the overall resistance and the diode threshold voltage (Vd). When the input voltage surpasses the
threshold (Vd), the load’s resistance decreases.
For instance, by setting Vd to 1.6 V, R to 0.1, and connecting to a current-limited power supply with
voltage limit set to 5 V and current limit to 300 mA, activating the input results in an input voltage of
approximately 1.6 V and a current of 300 mA. This corresponds to a resistance of 16 Ohms, signicantly
higher than the set value of 0.1 Ohms (refer to table 6.4).
Similar to the Constant Resistance (CR) mode, a resistance value is established to determine the slope
of the diode characteristic. For example, with a 3 V VD, 0.1 Ohms, and 1.38 A, the calculation yields 3
+ 0.1Ω ∗ 1.38 = 3.18.
Voltage Current Equivalent Load Resistance
1.00 0 innite
1.58 15 mA 105 Ohms
1.62 215 mA 7.5 Ohms
1.63 300 mA 5.4 Ohms
1.69 1 A (limit changed) 1.7 Ohms
Table 6.4 LED Mode Example
6.9.1 Congure LED Mode
Similar to CR Mode, the control system speed can make load switching power
supplies problematic.
To congure the LED test:
Step 1. Press the + to enter the LED State conguration menu.
Step 2. Use the navigation keys to select the ON option. Press the to enable the LED test.
Step 3. Use the numeric keypad to set the Vd. Press the to conrm the VD threshold.