TM 11-6625-2965-14&P
3-9 CHANGING CURRENT LIMIT
3-10 The current limit can be varied by adjusting resistor R81, located on the printed wiring board. This adjustment procedure is described in Paragraph 5-74. In Models 6204B and 6206B, the current limit may be reduced to a value lower than that attainable by adjusting R81, by adding an external resistor as shown in Figure 3-3. The approximate value of the external resistance (Rx) can be determined by using the following equation
R X = 1 . 7 5
IE
where: IE = the output current
RI = the internal current sampling resistance for the particular operating mode to be used.
1.75. the approximate voltage drop across the internal sampling resistance at the current limit crossover point.
NOTEThe power supply’s performance will be somewhat degraded if it is operated too close to (within 10OmA) the current limit crossover point.
A1 A2 A6 A7 A8 A9 -S – GND + +S A10
Figure 3-3. Current Limit Alteration
3-11 CONNECTING LOAD
3-12 Each load should be connected to the power supply output terminals using separate pairs of connecting wires. This will minimize mutual coupling effects between loads and will retain full advantage of the low output impedance of the power supply. Each pair of connecting wires should be as short as possible and twisted or shielded to reduce noise pickup. (If shield is used, connect one end to power supply ground terminal and leave the other end unconnected. )
3-13 If load considerations require that the output power distribution terminals be remotely located from the power supply, then the power supply output terminals should be connected to the remote distribution terminals via a pair of twisted or shielded wires and each load separately connected to the remote distribution termina1s. For this case, remote sensing should be used (Paragraph 3-25).
3-14 OPERATION BEYOND NORMAL RATED OUTPUT
3-15 Although the supply can deliver greater than the rated output on both the lower and higher voltage ranges without being damaged, it can not be guaranteed to meet all of its performance specifications . Generally when operating the supply in this manner, the output is unstable when connected to a load. When greater than the lower rated voltage is required, the higher voltage range should be used. This range will deliver half as much output current and all specifications will apply as listed in Table 1-1. However, if the line voltage is maintained above its nomina1 value, the supply will probably operate within specifications above its rated output.
3-16 OPTIONAL OPERATING MODES3-17 REMOTE PROGRAMMING, CONSTANT VOLTAGE
3-18The constant voltage output of the power supply can be programmed (controlled) from a remote location if required. Either a resistance or voltage source can be used for the programming device. The wires connecting the programming terminals of the supply to the remote programming device should be twisted or shielded to reduce noise pickup. The VOLTAGE controls on the front panel are disabled according to the following procedures .
3-19 Resistance Programming (Figure 3-4). In this mode, the output voltage will vary at a rate determined by the programming coefficient (200 ohms per Volt for Model 6204B and 6205B or 300 ohms per Volt for Model 6206 B). The output voltage will increase by 1 Volt for each 200 ohms (or 300 ohms) added in series with the programming terminals. The programming accuracy is 1% of the programmed voltage. If greater programming accuracy is required, it may be achieved by changing resistor R13 as outlined in Section V.
3-20 The output voltage of the power supply should be zero Volts ± 20 millivolts when zero ohms is connected across the programming terminals . If a zero ohm voltage closer than this is re- quired, it may be achieved by changing resistor R6 or R8 as described in Section V.
