times an initial pulse is triggered per second. You can determine whether you need the highest possible PRF value, or whether you are satisfied with a low value. You have 10 steps available for the setting; step 1 means the lowest PRF value.
The larger your workpiece, the smaller PRF values are needed in order to avoid phantom echoes. In the case of smaller PRF values, however, the A-scan update rate becomes lower; for this reason, high values are required if a workpiece should be scanned fast.
The best way to determine the suitable PRF value is by experimenting: start from the highest step and reduce the value until there are no more phantom echoes. Operation:
– Use v to select the function PRF-MOD and adjust the required value by means of the right-hand rotary knob.
Adjusting the pulser (function group PULS)
Operation
DUAL (Pulser-receiver separation)
You can activate the pulser-receiver separation in the function DUAL.
This function must be set to off in pulse-echo mode using a single-element probe. Set the function to on if you intend to work in through-transmission mode or with a dual-element (TR) probe.
Operation:
– Use v to select the function DUAL and set the function to on or off by means of the right-hand rotary knob.
The LED D (Dual) is lit with active DUAL function.
PRF-MOD (Pulse repetition frequency)
The pulse repetition frequency indicates the number of times an initial pulse is triggered per second. You can determine whether you need the highest possible PRF value, or whether you are satisfied with a low value. You have 10 steps available for the setting; step 1 means the lowest PRF value.The larger your workpiece, the smaller PRF values are needed in order to avoid phantom echoes. In the case of smaller PRF values, however, the A-scan update rate becomes lower; for this reason, high values are required if a workpiece should be scanned fast.
The best way to determine the suitable PRF value is by experimenting: start from the highest step and reduce the value until there are no more phantom echoes. Operation:
– Use v to select the function PRF-MOD and adjust the required value by means of the right-hand rotary knob.
Krautkramer USM 25 Issue 07, 07/2003 5-13
Operation
Adjusting the receiver (function group RECV)
5.5
Adjusting the receiver
(function group RECV)
You will find all functions for the adjustment of the pulser in the function group RECV.
– If required, use E to change the operating level. – Use u to select the function group RECV.
H Note:
Double assignment of the function FINE G / dBSTEP. For operation (changeover), please see the operation of the corresponding function.
FINE G (fine adjustment of gain)
This function serves for the fine adjustment of the current gain value. The fine adjustment is possible over a range of 40 steps within the range of approx. 4 dB. The displayed gain value will not change.
Adjustment range: -10 to +30 Operation:
– The function FINE G / dBSTEP has a double assignment (icon >). Toggle between the two functions by repeatedly pressing the corresponding key v.
– Use v to select the function FINE G, and then use the right-hand rotary knob to adjust the value for the fine gain.
Operation
Adjusting the receiver (function group RECV)
5.5
Adjusting the receiver
(function group RECV)
You will find all functions for the adjustment of the pulser in the function group RECV.
– If required, use E to change the operating level. – Use u to select the function group RECV.
H Note:
Double assignment of the function FINE G / dBSTEP. For operation (changeover), please see the operation of the corresponding function.
FINE G (fine adjustment of gain)
This function serves for the fine adjustment of the current gain value. The fine adjustment is possible over a range of 40 steps within the range of approx. 4 dB. The displayed gain value will not change.
Adjustment range: -10 to +30 Operation:
– The function FINE G / dBSTEP has a double assignment (icon >). Toggle between the two functions by repeatedly pressing the corresponding key v.
– Use v to select the function FINE G, and then use the right-hand rotary knob to adjust the value for the fine gain.
5-14 Issue 07, 07/2003 Krautkramer USM 25
Operation Adjusting the receiver (function group RECV)
dBSTEP
Use this function to set a step size for the gain vari- ation by means of the key V. The value set here is subsequently available to you as the sixth step for the stepwise gain variation. You have a free choice of the value within the setting range.
Operation:
Setting range: 6.5 to 20 dB
– The function FINE G / dBSTEP has a double assignment (icon >). Toggle between the two functions by repeatedly pressing the corresponding key v.
– Use v to select the function dBSTEP and set the value for the gain by means of the right-hand rotary knob.
REJECT
The function REJECT allows you to suppress unwanted echo indications, for example structural noise from your test object.
The % screen height setting indicates the minimum height that the echoes should attain in order for them to be displayed on the screen at all. The Reject setting cannot be higher than the lowest threshold setting (minus 1 %) of any gate.
Operation:
– Use v to select the function REJECT and set the required percentage value by means of the right-hand rotary knob.
A
Attention:You should handle this function with great caution, as it may of course happen that you suppress echoes from flaws as well. Many test specifications expressly forbid using the Reject function.
The LED R is therefore lit with active REJECT function.
Operation Adjusting the receiver (function group RECV)
dBSTEP
Use this function to set a step size for the gain vari- ation by means of the key V. The value set here is subsequently available to you as the sixth step for the stepwise gain variation. You have a free choice of the value within the setting range.
Operation:
Setting range: 6.5 to 20 dB
– The function FINE G / dBSTEP has a double assignment (icon >). Toggle between the two functions by repeatedly pressing the corresponding key v.
– Use v to select the function dBSTEP and set the value for the gain by means of the right-hand rotary knob.
REJECT
The function REJECT allows you to suppress unwanted echo indications, for example structural noise from your test object.
The % screen height setting indicates the minimum height that the echoes should attain in order for them to be displayed on the screen at all. The Reject setting cannot be higher than the lowest threshold setting (minus 1 %) of any gate.
Operation:
– Use v to select the function REJECT and set the required percentage value by means of the right-hand rotary knob.
A
Attention:You should handle this function with great caution, as it may of course happen that you suppress echoes from flaws as well. Many test specifications expressly forbid using the Reject function.
Krautkramer USM 25 Issue 07, 07/2003 5-15
Operation
FREQU (Frequency range)
In this function, you can adjust the operating frequency according to the frequency of your probe.
You have a choice between four frequency ranges: 0.2 – 1 MHz
0.5 – 4 MHz 0.8 – 8 MHz 2 – 20 MHz Operation:
– Use v to select the function FREQU and adjust the required value by means of the right-hand rotary knob.
Adjusting the receiver (function group RECV)
RECTIFY (rectification)
You can select the rectification mode of the echo pulses according to your application in the function RECTIFY. You have the following options to choose from:
• full-w (= full-wave) All half-waves are displayed above the baseline.
• pos hw (= positive half-wave) Only positive half- waves are displayed.
• neg hw (= negative half-wave) Only negative half- waves are displayed.
• rf (= radio frequency). Only applies to the display range up to 50 mm (steel).
Operation:
– Use v to select the function RECTIFY, and then use the right-hand rotary knob to adjust the required setting.
Operation
FREQU (Frequency range)
In this function, you can adjust the operating frequency according to the frequency of your probe.
You have a choice between four frequency ranges: 0.2 – 1 MHz
0.5 – 4 MHz 0.8 – 8 MHz 2 – 20 MHz Operation:
– Use v to select the function FREQU and adjust the required value by means of the right-hand rotary knob.
Adjusting the receiver (function group RECV)
RECTIFY (rectification)
You can select the rectification mode of the echo pulses according to your application in the function RECTIFY. You have the following options to choose from:
• full-w (= full-wave) All half-waves are displayed above the baseline.
• pos hw (= positive half-wave) Only positive half- waves are displayed.
• neg hw (= negative half-wave) Only negative half- waves are displayed.
• rf (= radio frequency). Only applies to the display range up to 50 mm (steel).
Operation:
– Use v to select the function RECTIFY, and then use the right-hand rotary knob to adjust the required setting.
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Operation
5.6
Setting the gates
(function groups aGAT and
bGAT)
All functions for setting the (dual) gate are arranged in the function group aGAT and bGAT.
– If required, use E to change the operating level. – Use u to select the function group aGAT or bGAT.
H Note:
If you have an instrument equipped with the Data Logger option at your disposal, you’ll be additionally able to use the C gate including all corresponding functions.