Heathkit Model EUW-16

Voltage Reference Source

 

Date Calibrated:   _____/_____/_____

 

Calibration Procedure

 

Ancillary Equipment Needed

 

VTVM

Null meter

Accurate Voltage Source

5 milliamp meter

20 milliamp meter

 

* * * * * * *

NOTES


ˇ         Remove all jumper wires between the circuit grounds and chassis ground.

 

ˇ         Remove all loads from both top terminals.

 

* * * * * * *

Initial Adjustments

 

(    )         Disconnect the line cord from the AC line voltage.

 

(    )         Set the OUTPUT switch to the AC OFF position.

 

(    )         Adjust the COARSE control to maximum counter-clockwise.

 

(    )         Adjust the FINE control to maximum counter-clockwise.

 

(    )         Set the RANGE switch to the X1 position.

 

(    )         Set the POLARITY switch to the NORMAL position.

 

* * * * * * *

Zener Diode and Voltage Regulator Tube Current

 

  The ZENER CURRENT and VOLTAGE REGULATOR (VR) TUBE adjustments have been preset at the factory. It should not be necessary to readjust these controls unless the CALIBRATE control setting has changed appreciably, either or both the VR tubes are replaced, or if the zener diode is replaced. Otherwise this section can be skipped.

 

(    )         Adjust the CURRENT ADJUST – ZENER control [back panel] to maximum counter-clockwise.

 

(    )         Adjust the CURRENT ADJUST – VR TUBE control [back panel] to maximum counter-clockwise.

 

(    )         Remove the outer case and set the instrument on its left side.

 

ˇ         The two test points A & B are on the four lug barrier strip on the right side of the inside back panel. Point B is the upper two lugs, while point A is the lower two lugs. Lug 1 of each test point pair is the lug closest to the center mounting tab.

 

 (    )        Disconnect the jumper at Test Point B [top two lug connections].

 

(    )         Connect the positive (+) lead of a 0–5 milliamp meter (Meter-1) to lug B1.

 

(    )         Connect the negative (–) lead of Meter-1 to lug B2

 

 (    )        Disconnect the jumper at Test Point A [bottom two lug connections].

 

(    )         Connect the positive (+) lead of a 0–20 milliamp meter (Meter-2) to lug A1.

 

(    )         Connect the negative (–) lead of Meter-2 to lug A2.

 

  The two shorting jumpers can be replaced using a single DPDT switch.

 

(    )         Connect the line cord to the AC line voltage.

 

(    )         Set the OUTPUT switch to the NORMAL position.

 

(    )  (    )1         Adjust the ZENER CURRENT control until Meter-1 indicates 2.4 ma.

 

(    )  (    )2         Adjust the VR TUBE control until Meter-2 indicates 16 ma.

 

(    )  (    )3         Adjust the CALIBRATE control using either the Method 1 or Method 2 section below.

 

(    )         Repeat the above three * adjustments until Meter-1 indicates 2.4 ma and Meter-2 indicates 16 ma.

 

(    )         Set the OUTPUT switch to the AC OFF position.

 

(    )         Disconnect the line cord from the AC line voltage.

 

(    )         Disconnect Meter-1 from Test Point B lugs 1 & 2.

 

(    )         Disconnect Meter-2 from Test Point A lugs 1 & 2.

 

(    )         Connect a shorting jumper across Test Point B lugs 1 & 2.

 

(    )         Connect a shorting jumper across Test Point A lugs 1 & 2.

 

(    )         Replace the outer case.

 

(    )         Skip down to the Final Front Panel Adjustments section.

 

* * * * * * *

Calibration Method 1

[Using an accurate voltage source]

 

(    )         Set the OUTPUT switch to the AC OFF position.

 

(    )         Set the front panel controls to match the voltage output of the accurate voltage source.

               (.1, 1, 10, or 100 volts)

 

(    )         Connect the accurate voltage source to the SIGNAL terminals of the VRS.

 

(    )         Connect either a VTVM or a null indicator to the OUTPUT terminals of the VRS.

 

(    )         Set the VTVM to the lowest usable range.

 

(    )         Press and hold the ZERO button on the VRS.

 

(    )         Adjust the Zero Adjust control on the VTVM so that it will indicate zero volts (null point) at some arbitrary reference position near mid-scale.

 

ˇ         The VTVM’s reference point must be equal to or greater than the calibration voltage.

 

(    )         Release the ZERO button on the VRS.

 

(    )         Adjust the CALIBRATE control [back panel], without pressing the ZERO button, to obtain the same zero voltage indication on either the VTVM or the null indicator.

 

  If it was necessary to readjust the output voltage more than approximately 1%, the settings of both the ZENER CURRENT ADJUST and the VR TUBE CURRENT ADJUST controls should be checked.

 

(    )         Skip down to the Final Front Panel Adjustments section.

 

* * * * * * *

Calibration Method 2

[Without an accurate voltage source]

 

(    )         Set the OUTPUT switch to the AC OFF position.

 

(    )         Adjust the COARSE control to 90.

 

(    )         Adjust the FINE control to 10.

 

(    )         Set the RANGE switch to the X1000 position.

 

(    )         Set the POLARITY switch to the NORMAL position.

 

(    )         Connect a VTVM to the OUTPUT terminals of the VRS.

 

(    )         Set the VTVM Range switch to 150 volts.

 

(    )         Set the OUTPUT switch to the STD VOLT position.

 

(    )         Adjust the CALIBRATE control until the VTVM indicates 100 volts.

 

  If it was necessary to readjust the output voltage more than approximately 1%, the settings of both the ZENER CURRENT ADJUST and the VR TUBE CURRENT ADJUST controls should be checked.

 

* * * * * * *

Final Front Panel Adjustments

 

(    )         Set the OUTPUT switch to the AC OFF position.

 

(    )         Set the RANGE switch to the X1 position.

 

(    )         Adjust the COURSE control to maximum counter-clockwise.

 

(    )         Adjust the FINE control to maximum counter-clockwise.

 

(    )         Disconnect all external components from the top terminals.

 

(    )         Disconnect the line cord from the AC line source.

 

(    )         Calibration procedure is complete.