K-Tec MT2000 User Manual

 

6                                                                                                                      MT2000-0200-01 Rev f (10-2007) 

DCN0160

 

 
The measurement principle using TDR is based on the fact that a dielectric constant discontinuity or geometric 
change  will yield a negative pulse having certain amplitude below the baseline. The greater the dielectric constant 
difference, the greater the negative amplitude of the return signal.  This means that a signal will show up on the 
baseline if there is a substantial change from a nozzle diameter to an open tank, for example, as signal plot at the 
process connection. This fact needs to be taken into account in order to configure the MT2000 properly (Consult 
section on commissioning). 
 
Displayed in Figure 2.1 is the return signal, as one would see it on an oscilloscope.  Refer to troubleshooting section 
for oscilloscope set up.  Abbreviations used are: 
 
GS 

Gain 

Setting 

    BLK 

Blanking 

THV 

Threshold Voltage 

 

 

 

URV 

Upper Range Value (20 mA) 

LRV 

Lower Range Value (4 mA) 

 

 

LL1 

Liquid Level 1 

L1 

Unmeasurable Zone (Top of Probe) 

 

L2 

Unmeasurable Zone (End of Probe) 

 
To effectively measure the level of very low dielectric products a different methodology is needed due to the poor 
reflection of the pulse on the surface of the product.  This reflection is not strong enough to make a reliable level 
measurement.  To achieve reliable and precise measurement the MT2000 uses the Ultra Low Dielectric (ULD) 
measurement method. This method requires the use of a flexible cable utilizing a weight / target assembly at the bot-
tom end of a precisely known length.  The pulse travels through the air at a known velocity and then passes through 
the product at a reduced velocity depending on the product dielectric constant. 
 
Note:  Reference Section 4.4.4 for ULD Mode setup and configuration.