Keithley 228A, Application & Reference Manual

Page 1: ...Advanced Test Equipment Rentals www atecorp com 800 404 ATEC 2832 Established 1981...

Page 2: ...Model 228A Voltage Current Source All references to the Model 228 apply also to the Model 228A 01985 Keithley Instruments Inc All rights reserved Cleveland Ohio U S A Document Number 228A 904 01...

Page 3: ...st 90 days LIMITATION OF WARRANTY This warranty does not apply to defects resulting from product modification without Keithley s express written consent or misuse of any product or part This warranty...

Page 4: ...C are present A good safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring Users of this product must be pnxecred from e cc ric shock at all times The...

Page 5: ...lly before performing the indicated procedure The CAUTION heading in a manual explains hazards that could damage the instrument Such damage may invalidate the warranty Insrmmentation and accessories s...

Page 6: ...Actually because of the Model 228 s precision and wide dynamic range the term SOURCE is used to differentiate it from or dinary power supplies Most power supplies do what the name implies they supply...

Page 7: ...load resistance A constant voltage source can deliver a voltage across a device almost independently of the load resistance Current Monitor The Model 228 output current is sensed internally and conve...

Page 8: ...he output terminals of the Model 228 therefore compensating for the test leads IR voltage drop Local sensing maintains regulation at the output terminals of the Model 228 Source Vice Sink Source is a...

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Page 10: ...e the Model 228 with the top and or bottom covers removed Lethal poten tials are present throughout the mainframe The covers must also be in place to allow proper air flow through the instrument Prope...

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Page 12: ...mple if the Model 228 is set for 5V IA a resistive load of lOs2draws lOOmA from the Model 228 In the operate mode the front panel display monitor shows 5 OOV and lOOA In this case the programmed param...

Page 13: ...anging output the programmed set ting is precise while the displayed value requires sufficient time to assme steady state For example if the output is programmed for l OOOV with no load the output wil...

Page 14: ...SETTING 1 2 kETTlNG 1OOsH OUT i 1OOpR lO RANGEl VSETTING SETTING OUT Figure 1 Model 228 Equivalent Output Circuit 9...

Page 15: ...he Model 228 is programmed to 1OV and lOA a load of more than 10 controls the current A load of less than IQ controls the voltage 1 lOVi2n 5A 2Q load requires 5A V 10A x 0 5Q 5V 0 5 7load requires 5A...

Page 16: ...STRUCTIVE LIMIT1 G 115 DESTRUCTIVE LIMIT B CURRENT L M T PROGRAMMED H C RRENT LlMlT PROGRAMMED C OLTAGE LIMIT PRDGRAMMED I VOLTAGE LIMIT t PROGRAMMED1 D CURRENT LIMIT PROGRAMMEDl J CURRENT LIMIT I PRO...

Page 17: ...e terminal and with proper polarity Connect S to the positive terminal and S to fhe negative terminal Improper polarity may result in S to fhe negative terminal Improper polarity may result in damage...

Page 18: ...Figure 4 Voltage Error Using Local Sensing 13...

Page 19: ...mount of overshoot under shoot and settling time or dynamic response for a changing load The Model 228 s load regulation can be calculated using the following two methods 1 As a Current Source Figure...

Page 20: ...different loads A 10 caused by different ILOADS x Ro For example lOOV 1A range voltage regulation for no load to full load A Vow 1A OA x 0 0100 O OlOV A VOUT O OlOV as a x 100 x 100 0 01 v0lJ r 1oov S...

Page 21: ...revious calibration constants may be used by pressing CANCEL while the Model 228 is displaying CAL nn External Current Monitor The current monitor can be used to obtain a faster and more accurate read...

Page 22: ...This method is very simple and requires no additional circuitry The second method involves some external circuitry A resistor in series with the output zener diode across the output could be used as a...

Page 23: ...Model 228 is ideal for testing such a wide ly used power transistor Refer to Figure 8 for V Ic curves for the 2N3055 Most Vc iIc curves illustrated in data manuals show the maximum safe forward bias...

Page 24: ...DWELL TIME1 Figure 8 Transistor ICNCE Curves For incoming inspection testing manual testing may not be cost effective The configura tion shown in Figure 7 may be connected to the IEEE 488 bus and a c...

Page 25: ...d values With the configura tion shown in Figure 9 the Nl N power transistor 2N3055 can be tested for several of its parameters Some of these tests inlcude l Secondary Breakdown VCE versus 1 l DC Curr...

Page 26: ...PROGRAM COMMENTS 336 PRI HT i i TIh EI OFF ALL lIlF THE TEST EQlJIF iEt IT 9 21...

Page 27: ...in the figure is rated at 1OV The Model 228 must be programmed for a voltage of less than 1OV to operate in the sink mode When the voltage of the Model 228 is less than the voltage of the battery cur...

Page 28: ...s or currents are forced upon them Figure 12 is a suggested protection circuit for the external power supply The two protection diodes in the circuit protect most supplies in the event one of the foll...

Page 29: ...obtained by 1OOV at 1A or 1OV at 10A In general this power is enough for most applications Sometimes however a higher voltage or a higher current that is outside of the Model 228 specifications is re...

Page 30: ...nt Figure 13 shows the method of connecting two Model 228s in series to obtain a higher voltage Figure 14 shows the recommended method of con necting more than two Model 228s in series to obtain a hig...

Page 31: ...own in Figure 16 The diodes allow the supplies to output current but not to sink current In Figures 15 and 16 the supplies are set for remote sense The amount of current is limited to the number of su...

Page 32: ...II 228 82 O r s w L Figure 15 Configuring Two Model 228s for Higher Current Figure 16 Configuring Three or More Model 228s for Higher Current 27...

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Page 34: ...t check one 0 Drifts 0 Unable to zero 0 Unstable 0 Will not read applied input 0 Overload D Calibration only 0 Data required 0 Certificate of calibration required attach any additional sheets as neces...

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