ABQ Industrial TI-25MX Operating Manual

Also see for TI-25MX: Instruction manual

Contents

ABQ Industrial TI-25MX Operating Manual Manual pdf 15 page image

–14 –5.0 MAKING MEASUREMENTSThe steps involved in making measurements are detailed in this section. The followingsections outline how to setup and prepare your TI-25MX for field use.An automatic or manual zero must always be performed. The auto zero is an ‘off block’electronic zero that does not require a zero reference standard. This will most always bethe zero option of choice, as it makes the zeroing process very easy and convenient toperform. However, the manual zero option offers better accuracy in terms of a referencepoint. If the manual zero option is enabled, the probe zero must be measured on thereference disk (battery disk) attached to the top of the instrument. The zero compensatesfor variations in the transducer. In either mode the sound velocity must be determined,and is used to convert the transit time to a physical length. The sound velocity can beselected from a material chart in the manual, selected from a short list of commonmaterials in the TI-25MX, or for greater precision determined from a sample of the testmaterial that has been mechanically measured. To enter the velocity from a table, lookup the material on the chart in the appendix of this manual and refer to the section belowon Calibration to a Known Velocity. To determine the velocity of a single sample, referto the Material Calibration section in section 5.2.When measuring curved materials, it’s more accurate to calibrate from two test points,one at the minimum limit of the target thickness and one at the maximum limit. In thiscase the reference disk mounted to the TI-25MX is not used. This is called two-pointcalibration and is described section 5.25.1 Probe zeroSetting the zero point of the TI-25MX is important for the same reason that setting thezero on a mechanical micrometer is important. It must be done prior to calibration, andshould be done throughout the day to account for any temperature changes in the probe.If the TI-25MX is not zeroed correctly, all the measurements taken may be in error bysome fixed value. The zero can only be performed with the measurement mode set topulse-echo (P-E). Therefore, if the TI-25MX is to use the echo-echo (E-E) measurementmode and a manual zero is being performed, the TI-25MX will argue by brieflydisplaying the message “NO PRB0”.IMPORTANT NOTE: The internal zero setting of the TI-25MX, used for the autozero mode, can be reset at anytime by performing a “manual zero”, and immediatelyfollowed by performing an “auto zero”.The TI-25MX is equipped with two zero options:1. Off Block Zero (Automatic Probe Zero) – When this feature is enabled theTI-25MX will do an electronic zero automatically, eliminating the need for a zerodisk or reference standard.