Design Features
The Type DB Vacuum Reference Tube is an evacuated, sealed vacuum gauge tube accurately calibrated to precisely simulate a gauge tube at a given operating pressure. It is electrically equivalent to the metal and glass gauge tubes used with Hastings Instruments. It permits quick and easy recalibration of Hastings Vacuum Gauge Indicators by merely plugging the instrument into the reference and adjusting the calibration ?current set? potentiometer until the instrument reads the exact pressure noted on the reference. The Type DB Vacuum Reference Tubes are available equivalent to most Hastings Gauge Tubes.

Application
Hastings Vacuum Gauge Indicators, Controllers, or Recorders can be checked or recalibrated in seconds by merely plugging the gauge tube cable into the reference tube. If calibration adjustment is necessary, the ?Current Set? potentiometer is adjusted until the instrument indicates the pressure marked on the vacuum reference tube. The customer now knows his instrument is correctly calibrated.

Whenever cable lengths between gauge tube and instrument are changed, some error may be introduced, requiring that the instrument be readjusted to compensate for any losses involved. By plugging the DB Vacuum Reference Tube into the new cable and readjusting the instrument for a correct reading, this ?error? is eliminated.

Selection
Choose the vacuum reference tube that is equivalent to the glass or metal Hastings Gauge Tube you are now using. The vacuum reference tube will be matched and sealed at a pressure falling on the lower portion of the scale and calibrated accurately at this exact pressure. For example, if an instrument uses a DV-6M Gauge Tube, a DB-20 Reference Tube is ordered. If a customer receives a reference tube marked ?at 10 mTorr?, this is the pressure to which the indicator should be adjusted when plugged into the vacuum reference tube.

Construction
The Type DB Vacuum Reference Tubes employ the same Hastings noble metal thermopile used in all Hastings Thermopile Vacuum Gauge Tubes. The thermopile is sealed in a glass capsule that has been evacuated, baked, outgassed, sealed, and then aged to ensure stability over long periods of time. The sealed capsule is then housed in a protective metal shell to provide a rugged, trouble-free assembly.

Calibration
Considerable care and time are required in the manufacture to obtain the high degree of precision and stability required for the vacuum reference tube.

The Type DB vacuum reference tube maintains its calibration over long periods of time. However, for applications requiring the highest possible degree of accuracy, a periodic return of the reference tube to the factory for a check and recalibration may be desirable. An annual or semiannual check assures the customer of an accurate and reliable reference at all times.