DAKOTA ULTRASONICS DFX-7 Operation Manual

Also see for DFX-7: Operation manual Manual

Contents

DAKOTA ULTRASONICS DFX-7 Operation Manual Manual pdf 51 page image

43CHAPTER SIXMAKING MEASUREMENTSThe steps involved in making measurements are detailed in this section. Thefollowing sections outline how to setup and prepare your DFX-7 for field use.An automatic or manual zero must always be performed. The auto zero is an offblock electronic zero that does not require a zero reference block. This will mostalways be the zero option of choice, as it makes the zeroing process very easy andconvenient to perform. However, If the manual zero option is enabled, the probezero must be measured on the reference disk (battery disk) attached to the top of theinstrument. The zero compensates for variations in the transducer. In all modes thesound velocity must be determined. The sound velocity is used to convert the transittime to a physical length. The sound velocity can be selected from a material chart inthe manual, selected from a material list in the DFX-7, or for greater precisiondetermined from a sample of the test material that has been mechanically measured.To enter the velocity from a table, look up the material on the chart in the appendix ofthis manual and refer to the section below on Calibration to a Known Velocity. Todetermine the velocity of a single sample, refer to the Material Calibration section onpage 53.When measuring curved materials, it is more accurate to calibrate from two testpoints, one at the minimum limit of the target thickness and one at the maximum limit.In this case the reference disk mounted to the DFX-7 is not used. This is called two-point calibration and is described on page 55.6.1 Auto Probe Recognition & Selecting the Transducer TypeThe first step in using the DFX-7 is to plug the transducer into the gauge and powerthe unit up. The DFX-7 has a special built-in automatic probe recognition feature thatwill check to see if the probe plugged into the gauge is an auto recognized probetype. If so, the DFX-7 will display a message indicating the transducer type and askthe user for confirmation to use the identified probe. If the transducer is not an autorecognized probe, the DFX-7 will display a message indicating the transducer typehas not been recognized, and force the user to select a transducer type from a list oftransducers according to frequency and diameter. Whether the transducer is autorecognized or selected from a predefined list, the DFX-7 will recall specific propertiesabout the transducer. Note: Once the transducer has been selected, the DFX-7 willstore and recall this transducer type every time the DFX-7 is powered on/off. Thetype will only change if the user physically selects another type from the list, orselects a previously saved setup. Therefore, if you have previously gone through thissection and selected the transducer you are using, proceed to the next section. Usethe following steps to select your transducer type. Note: If the transducer is notidentified on power up, be sure the transducer type selected is the same as thetransducer plugged into the DFX-7. Failure to do this will result in erroneousmeasurements: