ZH instruments SM-30 User manual

ZH instruments
Magnetic susceptibility meter
SM-30
USER’S MANUAL
Publication Date: June 2010

ADDRESS
Zdeněk Hůlka
ZHinstruments
Kárníkova 22
621 00 Brno
Czech Republic
Tel. + Fax: +420 - 541634297
GSM.: +420 - 603795973
E-mail: [e-mail]
Web: www.zhinstruments.cz

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1.GENERAL INFORMATION...................................................... 4
1.1 Application........................................................................... 4
1.2 Specification ........................................................................ 5
2. DESCRIPTION OF INSTRUMENT .......................................... 6
2.1 General description............................................................... 6
2.2 Operating principles.............................................................. 7
2.2.1 Basic modes A and B ...................................................................... 8
2.2.2 Extrapolation mode........................................................................ 9
2.2.3 Interpolation mode ...................................................................... 10
2.2.4 Scanning mode............................................................................. 10
2.2.5 Averaging mode ........................................................................... 11
2.2.6 Comparison of modes................................................................... 11
3. OPERATION....................................................................... 14
3.1 Switching instrument ON and OFF .........................................14
3.2 Setting and indication of mode ..............................................15

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3.3 Measuring susceptibility of rock .............................................15
3.3.1 Basic modes A, B.......................................................................... 15
3.3.2 Extrapolation mode...................................................................... 16
3.3.3 Interpolation mode ...................................................................... 17
3.3.4 Scanning mode............................................................................. 19
3.3.5 Averaging mode ........................................................................... 21
3.4 Memory registers ................................................................22
3.5 Battery replacement ............................................................24
3.6 Communication with computer ..............................................25
3.6.1 General information ..................................................................... 25
3.6.2 Instrument operation using computer.......................................... 25
3.6.3 Transfer of data to computer........................................................ 26
3.7 Error messages ...................................................................28
4 FIGURES............................................................................. 30
4.1 Figure 1 .............................................................................30
4.2 Figure 2 .............................................................................31
4.3 Figure 3 .............................................................................32
4.4 Figure 4 .............................................................................33
4.5 Figure 5 .............................................................................34

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4.6 Figure 6 .............................................................................35
4.7 Figure 7 .............................................................................36
5.APPENDICES ...................................................................... 37
5.1 SM30 software ....................................................................37
5.2 SM30 programme for Windows 95/98/NT/2000 .......................37
5.2.1 Running the program ................................................................... 37
5.2.2 Reading memory registers ........................................................... 38
5.2.3 Communicating with the computer on-line................................... 38
5.2.4 Handling the charts...................................................................... 39
5.2.5 Saving the data ............................................................................ 40
5.3 Finite thickness layer correction ............................................41
5.4 Conductivity effect...............................................................42
5.5 The demagnetisation factor correction....................................44
5.6 Drill Core correction factor ....................................................45

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1.GENERAL INFORMATION
1.1 Application
The SM-30 meter is intended for measuring the magnetic susceptibility of rock.
Owing to its high sensitivity, it is capable of measuring rock with a very low
susceptibility. It can also measure diamagnetic substances. The meter reaches its
peak sensitivity within a very few seconds after switch-on. By employing a very
sophisticated way of processing the signal, the meter can efficiently reduce the
influence of external electromagnetic disturbances and the noise of electronic
circuits. Its low wei
g
ht and small size make this instrument ideal for use
out-of-doors.

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1.2 Specification
SENSITIVITY…………………………………………………………………………………….1x10-7 SI Units
MAX MEASURED VALUE…………………………………………………………………………………..….1SI
DIMENSIONS……………………………………………………………….……………..100 x 65 x 25 mm
WEIGHT………………………………………………………………………………………….……………0.150 kg
OPERATING FREQUENCY………………………………………………………………………………..…8kHz
MEASUREMENT TIME
…………………………………………………………………………………….basic mode approx. 5s
…………………………………………………………………..drift correction modes approx. 8s
DIGITAL DISPLAY………………………………………………………………….LCD 4digit,10mm high
CONTROLS…………………………………………………………………………………………3 push buttons
DATA MEMORY………………………………………………………………….up to 250 measurements
PICK-UP COIL SIZE 50 mm in diameter
OPERATING TEMPERATURE……………………………………………………………..-20oC to +50oC
BATTERY……………………………………………………………….….…….2 Lithium 3V type CR2430
BATTERY LIFE…………………………………………………………….………………..typically 80 hours
COMMUNICATION WITH COMPUTER……………………………………………………………..RS232

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2. DESCRIPTION OF INSTRUMENT
2.1 General description
The susceptibility meter is enclosed in a box, which has a front panel with push
buttons and a four-digit 10mm character display. In order to get the right value
in SI, the user must multiply the reading by a constant 10-3.
Behind the front panel there is a buzzer, which monitors by way of acoustics the
operation of the meter. On the right-hand side of the cover there is a connector
for communication with a computer. A communication cable is delivered as part
of the set. On the bottom side of the cover there is a little cubicle holding two Li
batteries.
The 50mm pickup coil is placed on the left-hand side parallel with the bottom
part of the cover (see figure 6).

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2.2 Operating principles
The meter contains an oscillator with a pickup coil. The frequency of the oscillator
depends on the distance of the meter from rock. the change in frequency is
proportional to the amount of susceptibility of the rock. In order to find out about
the change, it is necessary to measure the oscillator frequency twice. The first
measurement is performed near the rock. This is called pick-up step.
The second measurement is carried out when the meter is away from the rock
(free air measurement). The second phase is called compensation step.
After the second step is finished, both values are subtracted and displayed. Both
the steps are initiated by the operator.
The above mentioned mode is called basic mode or mode 1.
When measuring rock of very low susceptibility, it is possible that the oscillator
thermal drift becomes greater than the effect of the rock. In this case it is
necessary to measure not only the susceptibility, but also the thermal drift. The
thermal drift and susceptibility values are then compared. The thermal drift
measurement requires that two measurements away from rock are carried out,
which means that there have to be three steps altogether. Two steps are
performed without rock and one is performed with rock. The SM-30 meter offers
two ways of correcting the drift. The first mode is called extrapolation mode or
mode 2.

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The second mode is called interpolation mode or mode 3.
When measuring places that are situated very close to one another, it is best to
use scanning mode.
This mode corrects the thermal drift as well and the measurement is very quick,
although the drift correction is not so precise as in the extrapolation or
interpolation mode.
2.2.1 Basic modes A and B
The function of the meter is shown in Figure 1a. Figure 1b shows the way the
oscillator frequency is affected by the measured object. It also shows the
frequency difference in both the steps. The difference is used as ground for the
calculation of magnetic susceptibility. Figure 1 deals with an ideal case, when
there is no thermal drift. Susceptibility is calculated using the formula
susc = f2- f1
After the compensation step is finished, the value susc is displayed.
Figure 2 shows the effects of thermal drift during Basic mode. It shows that the
oscillator frequency is not only influenced by the measured rock during the
pickup step, but it changes without any apparent reason and causes
measurement error.

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The SM-30 has two basic modes A and B. The only difference between modes A
and B is in the length of the pick-up and compensation steps. The basic mode B
has these steps 4 times faster than mode A. Mode B is suitable for measuring
medium and high susceptibility.
2.2.2 Extrapolation mode
Thermal drift correction is described in Figure 3. The time elapsed during the
pickup step and the first compensation step depends on the operator. The time
lag between the second and first compensation steps is set automatically and it is
tas well. It is then quite easy to measure the value of drift.
drift = f3- f2
It is valid that
susc + drift = f2- f1
Furthermore
susc = f2- f1- (f3- f2) = 2f2- f1- f3

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The correction of drift is performed automatically according to the last equation.
After the first compensation step is finished, the display shows first the
uncorrected f2- f1value. After the second compensation step is finished, the
value is corrected and the display shows the value 2f2- f1- f3.
2.2.3 Interpolation mode
This method requires that the user put the meter near rock during the second
step. The first and third steps are compensation steps. The third step of this
mode (the second compensation step) is initiated automatically. Figure 4 makes
it possible to derive
susc = (f1+ f3)/2 - f2= -1/2 (2f2- f1-f3)
The reading is corrected after the second compensation step and the display
shows the value -1/2 (2f2- f1- f3).
2.2.4 Scanning mode
The principle is clear from Figure 5, which shows the block of measurement. The
first and last steps are compensation (free air). The first compensation step is
initiated by the left button. Afterwards come pickup steps (near the rock), which
are started by the left button as well. The measurement is finished with the
second compensation steps, initiated by the middle button. The display shows

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after each pickup step the susceptibility value, calculated similar to the Basic
mode. This calculation takes into consideration the value measured during the
first compensation step fc1. The susceptibility is stored in the operation memory
of the processor together with the time elapsed since the first compensation step
(see Figure 5). After performing the second - final - compensation step (middle
button), drift correction is made using interpolation. The corrected susceptibility
values are stored in memory registers to be displayed in the usual manner.
The total number of pickup steps in one block is 20. After the 20th pick-up step
the instrument warns the operator that measured block has to be terminated by
second compensation step.
2.2.5 Averaging mode
This mode is very similar to Scanning mode (mode 4). The only difference is in
the very end of measuring procedure. After the middle button is pressed and
drift correction is done, the average value is calculated and put into memory
register (see Figure 5).
2.2.6 Comparison of modes
Both basic modes are simple and yet applicable in most situations. Basic mode B
is suitable for medium and high susceptibility. Extrapolation mode is useful when
measuring low susceptibility rock. The operation of the meter is the same as
during the Basic mode, only the correction of the final value takes a few seconds
longer.

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The advantages of the interpolation method can be seen in the equations in 2.2.2
and 2.2.3. A comparison of both calculations shows that the Interpolation mode
requires the result to be divided by -2. This means that the value is twice as
precise as with the extrapolation method. The correct value is obtained by
processing the data in the same way as with extrapolation method and dividing it
by -2.
The interpolation method offers twice as effective noise reduction as the
extrapolation method. It is, however, less similar to the basic modes used in
most measurements.
The interpolation method is useful when dealing with samples of very low
susceptibility.
The scanning mode is best in such cases as measuring a number of points on a
profile. Core is a good example. In order to measure nvalues it is necessary to
measure the frequency n+2 times, while during extrapolation or interpolation
method it is necessary to perform 3n measurements.
The disadvantage of the scanning mode lies in the lesser ability to reduce drift.
This is especially the case when the number of pickup steps between two
compensation steps is too high.
Due to the lower reduction of drift, the readings are displayed with the definition
of 10-6 SI.
The following table makes it possible to compare the six usual modes.

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object
measurement
&
init.
object
measurement
&
init.
object
measurement
&
init.
resolution
[SI Units]
basic modes*)
A & B
rock
press left button
free air
press left button
- - - - -
- - - - -
10-6
extrapolation
mode
(drift correction)
rock
press left button
free air
press left button
free air
automatically 10-7
interpolation
mode
(drift correction)
free air
press left button
rock
press left button
free air
automatically 10-7
scanning mode free air
press left button
rock n-times
press left button
free air
press right button 10-6
averaging mode free air
press left button
rock n-times
press left button
free air
press right button 10-7
*) Basic mode B has 4 times faster measuring time than basic mode A.

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3. OPERATION
3.1 Switching instrument ON and OFF
The meter is switched on by pressing the middle button. The meter displays
within 0.2 seconds of switchon the mode number used before the meter was
switched off. After the button is released, the last susceptibility value is displayed
and the buzzer gives a short beep. The modes are numbered as follows:
basic mode A…...........…………………………………………………………..…….………….……..…-1--
extrapolation mode………………………………………………………………………………………..…..-2--
interpolation mode…….………………………………………………………..………………………….….-3--
scanning mode…………………………………………………………………………………………..........-4--
averaging mode….……………………………………………………………………………………..........-5--
basic mode B.............…………………………………………………………...…….…….….……..…-6--
The respective modes are given the same numbers during the setting up of
modes (see next chapter).
The meter is switched off by pressing the left button and holding it until the
buzzer gives a short bee
p
to indicate switchoff. The time is a
pp
roximatel
y
5 seconds. The meter also displays the word OFF. After the button is released,
the display goes off and the meter is off as well.

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The meter switches itself off after no button has been pressed for three minutes.
The meter gives a beep to indicate switchoff.
3.2 Setting and indication of mode
By pressing the right button first and then pressing the left button without
releasing the right one the user can display the number of mode according to the
table in the previous chapter. By pressing the left button a second time, the user
sets up a mode with a number greater by 1. Mode 6 is followed by mode 1. After
finishing this procedure, the set mode is used.
3.3 Measuring susceptibility of rock
3.3.1 Basic modes A, B
If necessary, switch the instrument into the Basic mode indicated by –1-- or by
–6--. The only difference between modes A and B is in the length of the pick-up
and compensation steps. The basic mode B has these steps 4 times faster than
mode A.
The switched on meter is put near the rock and the operator presses the left
button. The meter gives a high-pitched beep and when the operator releases the
button, the meter is performing the pickup step, or measuring frequency near
rock. During the frequency measurement the buzzer is giving a low-pitched beep.
The display shows the middle three horizontal segments. The pickup step takes

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approximately 2 seconds. After the pickup step is finished, the buzzer goes silent
and the number of the memory register prepared to store the value is displayed.
Now the operator removes the meter from the rock and presses the left button.
The buzzer is emitting a high-pitched beep. After the button is released, the
meter is performing the compensating step, which means - in this case - one
measurement away from the rock. During the frequency measurement the
buzzer is giving a low-pitched beep and the three middle horizontal segments are
displayed. The compensating step is as long as the pickup step, that is 2
seconds. The buzzer goes silent when this step is finished and the value of
magnetic susceptibility is displayed. The displayed value must be multiplied by
10-3 to be according to the SI.
Basic mode displays readings with the resolution of 10-6 SI.
3.3.2 Extrapolation mode
If necessary, switch the instrument into the Extrapolation mode indicated by -2--
The switched on meter is put near the rock and the operator presses the left
button. The meter gives a high-pitched beep and when the operator releases the
button, the meter is performing the pickup step, or measuring frequency near
rock. During the frequency measurement the buzzer is giving a low-pitched beep.
The display shows the middle three horizontal segments. The pickup step takes
approximately 2 seconds. After the pickup step is finished, the buzzer goes silent
and the number of the memory register prepared to store value is displayed.

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Now the operator removes the meter from the rock and presses the left button.
The buzzer is emitting a high-pitched beep. After the button is released, the
meter is performing the first compensating step, which means frequency
measurement away from the rock. During the frequency measurement the
buzzer is giving a low-pitched beep and the three middle horizontal segments are
displayed. The frequency measurement is as long as the pickup step, that is
approximately 2 seconds. The buzzer goes silent when this step is finished and
the measured value is displayed. The same value would constitute the final
reading when measuring in the Basic mode. Now the operator holds the meter
away from the rock. In a few seconds, the buzzer starts giving a low-pitched
beep to indicate the second compensating step, which means the second
frequency measurement away from the rock. After the step is finished, the
corrected value of magnetic susceptibility is displayed. The obtained value is not
affected by the linear part of drift. The displayed value must be multiplied by 10-3
to be according to the SI.
Extrapolation mode displays readings with the resolution of 10-7 SI.
3.3.3 Interpolation mode
If necessary, switch the instrument into the Interpolation mode, indicated by -3-
Now the operator removes the meter from the rock and presses the left button.
The buzzer is emitting a high-pitched beep. After the button is released, the

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meter is performing the first compensating step, which means frequency
measurement away from the rock. During the frequency measurement the
buzzer is giving a low-pitched beep and the three middle horizontal segments are
displayed. The first compensating step is approximately 2 seconds long. The
buzzer goes silent when this step is finished and the number of the memory
register prepared to store value is displayed.
The meter is now put near the rock and the operator presses the left button
again. The buzzer gives a high-pitched beep and when the operator releases the
button, the meter is performing the pickup step, or measuring frequency near
the rock. During the frequency measurement the buzzer is giving a low-pitched
beep. The display shows the middle three horizontal segments. The pickup step is
as long as the first compensating step, that is approximately 2 seconds. After the
frequency measurement is finished, the buzzer goes silent and the measured
value is displayed. The same value would constitute the final reading when
measuring in the Basic mode. Now the operator holds the meter away from the
rock. In a few seconds, the buzzer starts giving a low-pitched beep to indicate
the second compensating step, which means the second frequency measurement
away from the rock. After the step is finished, the corrected value of magnetic
susceptibility is displayed. The obtained value is not affected by the linear part of
drift. The result must be multiplied by 10-3 to be in the SI units. Interpolation
mode displays readings with the resolution of 10-7 SI.