HP 3478A Multimeter
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 Introduction:

   This instrument  module provides GPIB programming support for the HP
   3478A  Multimeter.  It  contains  functions	for  opening,  configuring,
   taking measurements from, and closing the instrument via the GPIB.
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  Assumptions:

    To successfully use this module, the following conditions must be met:

      - the HP3478A is connected to the GPIB.
      - the GPIB address supplied to the initialize function must match
	the GPIB address set via the dipswitches on the rear of the
	instrument.
      - there is one unused device name in the handler.
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  LabWindows Libraries:

    In	order to use this instrument module outside of the LabWindows envi-
    ronment, it must be linked with the following LabWindows libraries:

      - Formatting and I/O
      - GPIB
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  Error Codes:

    All  error codes are  returned  in a global integer variable:

		hp3478a_err

    A program should examine this variable after each function call is made
    to determine if any errors occurred.
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  Function Tree Layout:

    Initialize
    Initial Setup
    Configure and Measure
    Configure
    Measure
    Close
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  Function	     : Initialize

  C Syntax	     : void hp3478a_init(Addr);
		       int Addr;

  Purpose	     : Initializes the hp3478a on the GPIB and resets the
		       instrument to its power-on default state.

  Parameter List     : Addr - GPIB Address (0 to 30)

  C Example	     : hp3478a_init(23);

  Error Codes	     : The valid error codes for this function are:
			   0 : Success
			  -1 : GPIB Address out of range
			 220 : Unable to open instrument
			 230 : GPIB write error
			 233 : Unable to configure GPIB address
			 235 : Unable to clear device
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  Function	     : Initial Setup

  C Syntax	     : void hp3478a_init(autozero, display_fun, message);
		       int autozero, display_fun;
		       char *message;

  Purpose	     : Enables/disables the autozero mode and permits
		       a message to be displayed in the 3478A display.

  Parameter List     : autozero - enable/disable the autozero mode
			   0 : autozero off
			   1 : autozero on

		       display_fun -
			   1 : normal display
			   2 : user specified display

		       message - variable containing the string to be
				 displayed (12 char. max; no spaces)

  C Example	     : hp3478a_init(0, 2, "AN_EXAMPLE");

  Error Codes	     : The valid error codes for this function are:
			   0 : Success
			  -1 : Autozero out of range
			  -2 : Display function out of range
			 230 : GPIB write error
			 231 : GPIB read error
			 232 : Instrument not initialized

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  Function	     : Configure

  C Syntax	     : void hp3478a_config(fun,range,trigger);
		       int fun, range, trigger;

  Purpose	     : Configures the function, range, and trigger
		       parameters of the meter.

  Parameter List     : fun - meter function
			 1 : DC Volts
			 2 : AC Volts
			 3 : 2 wire Ohms
			 4 : 4 wire Ohms
			 5 : DC current
			 6 : AC current
			 7 : Extended Ohms

		       range - measurement range
			-3 : Autoranging
			-2 : 30 mV
			-1 : 300 mV/mA
			 0 : 3 V/A
			 1 : 30 V/Ohms
			 2 : 300 V/Ohms
			 3 : 3K Ohms
			 4 : 30K Ohms
			 5 : 300K Ohms
			 6 : 3M Ohms
			 7 : 30M Ohms

		       trigger - trigger mode
			 1 : Internal trigger
			 2 : External trigger
			 3 : Single trigger
			 4 : Trigger hold
			 5 : Fast trigger

  C Example	     : hp3478a_config(1,-3,1);

  Error Codes	     : The valid error codes for this function are:
			   0 : Success
			  -1 : Function out of range
			  -2 : Range out of range
			  -3 : Trigger out of range
			 230 : GPIB write error
			 232 : Instrument not initialized

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  Function	     : Measure

  C Syntax	     : void hp3478a_measure(reading);
		       double *reading;

  Purpose	     : Reads the current measurement value from the meter.

  Parameter List     : reading- a real variable in which the value of
				the measurement is returned.

  C Example	     : double reading;

		       hp3478a_measure(&reading);

  Error Codes	     : The valid error codes for this function are:
			   0 : Success
			 231 : GPIB read error
			 232 : Instrument not initialized
			 235 : Unable to trigger instrument
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  Function	     : Configure and Measure

  C Syntax	     : void hp3478a_full(fun,range,trigger,reading);
		       int fun, range, trigger;
		       double *reading;

  Purpose	     : Configures the meter and then reads the current
		       measurement value.

  Parameter List     : fun - meter function
			 1 : DC Volts
			 2 : AC Volts
			 3 : 2 wire Ohms
			 4 : 4 wire Ohms
			 5 : DC current
			 6 : AC current
			 7 : Extended Ohms

		       range - measurement range
			-3 : Autoranging
			-2 : 30 mV
			-1 : 300 mV/mA
			 0 : 3 V/A
			 1 : 30 V/Ohms
			 2 : 300 V/Ohms
			 3 : 3K Ohms
			 4 : 30K Ohms
			 5 : 300K Ohms
			 6 : 3M Ohms
			 7 : 30M Ohms

		       trigger - trigger mode
			 1 : Internal trigger
			 2 : External trigger
			 3 : Single trigger
			 4 : Trigger hold
			 5 : Fast trigger

		       reading - a real variable in which the value of
				 the measurement is returned.

  C Example	     : double reading;
		       hp3478a_full(0,0,0,&reading);

  Error Codes	     : The valid error codes for this function are:
			   0 : Success
			  -1 : Function out of range
			  -2 : Range out of range
			  -3 : Trigger out of range
			 230 : GPIB write error
			 231 : GPIB read error
			 232 : Instrument not initialized
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  Function	     : Close

  C Syntax	     : void hp3478a_close();

  Purpose	     : Effectively disconnects the hp3478a from the GPIB
		       and returns the instrument to local mode.

  Parameter List     : NONE

  C Example	     : hp3478a_close();

  Error Codes	     : The valid error codes for this function are:
			   0 : Success
			 221 : Unable to close instrument
			 232 : Instrument not initialized
			 234 : Unable to place instrument in local mode
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