Checkline TI-25MX, Operating Manual

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5.0  MAKING MEASUREMENTS

The steps involved in making measurements are detailed in this section. The following 
sections 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 be 
the zero option of choice, as it makes the zeroing process very easy and convenient to 
perform. However, the manual zero option offers better accuracy in terms of a reference 
point. If the manual zero option is enabled, the probe zero must be measured on the 
reference disk (battery disk) attached to the top of the instrument. The zero compensates 
for 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 be 
selected from a material chart in the manual, selected from a short list of common 
materials in the TI-25MX, or for greater precision determined 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 of this manual and refer to the section below 
on Calibration to a Known Velocity. To determine the velocity of a single sample, refer 
to 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 this 
case the reference disk mounted to the TI-25MX is not used. This is called two-point 
calibration and is described section 5.2

5.1   Probe zero

Setting the zero point of the TI-25MX is important for the same reason that setting the 
zero on a mechanical micrometer is important. It must be done prior to calibration, and 
should 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 by 
some fixed value.  The zero can only be performed with the measurement mode set to 
pulse-echo (P-E). Therefore, if the TI-25MX is to use the echo-echo (E-E) measurement 
mode and a manual zero is being performed, the TI-25MX will argue by briefly 
displaying the message “NO PRB0”. 

IMPORTANT NOTE: 

The internal zero setting of the TI-25MX, used for the auto 

zero mode, can be reset at anytime by performing a “manual zero”, and immediately 
followed 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 the    
 

TI-25MX will do an electronic zero automatically, eliminating the need for a zero  

disk or reference standard.