KMAG4 - 260MHz Four-Sensor Magnetometer Counter
Features
Absolute Resolution
R = B / (f * T), where
R - the resolution in nT
B - the magnetic field in nT
T - The measurement cycle in ms
f - The reference frequency in Hz
As can be seen from the above formula, the absolute resolution depends on the reference frequency, magnetic field value and the sample time. Better resolution will be achieved if a higher reference frequency is used. The magnetic field value and the sample time should be defined explicitly when specifying the absolute resolution. Otherwise the numbers could be mislieading. It is not uncommon for a manufacturer to claim for example that their counter has a resolution of 0.1pT without mentioning anything else. The number in such a case has most likely been calculated using the lowest magnetic field value and the longest sample time, because this case provides the best number for the resolution.
Below is a table that shows the KMAG4 - 260MHz counter resolution compared to the resolution of a 100MHz counter at different sample rates and different magnetic fields.
| B[nT] | 10000 | 50000 | 100000 | |
|---|---|---|---|---|
| 1s/sec | f=100MHz | 0.1 | 0.5 | 1 |
| f=260MHz | 0.038 | 0.192 | 0.385 | |
| 10s/sec | f=100MHz | 1 | 5 | 10 |
| f=260MHz | 0.385 | 1.92 | 3.85 | |
| 20s/sec | f=100MHz | 2 | 10 | 20 |
| f=260MHz | 0.769 | 3.85 | 7.69 | |
| 50s/sec | f=100MHz | 5 | 25 | 50 |
| f=260MHz | 1.92 | 9.62 | 19.2 | |
| 100s/sec | f=100MHz | 10 | 50 | 100 |
| f=260MHz | 3.85 | 19.2 | 38.5 |
As can be seen from the above table, KMAG4 provides far better resolution than the 100MHz counters, even at twice the sampling rates. Even better - the table above shows that KMAG4 provides better resolution while sampling 50 times per second, than the 100 MHz counters sampling at only 20 times per second.
Gradiometer Applications
Contains four counters in the same box and can process the signals from up to four caesium sensors. The four counters use the same reference frequency, providing exactly the same readings for all the four channels if the same signal is connected to them. The higher resolution and the common reference frequency for the four counters make the instrument perfect for gradiometer applications.
Fast
Can provide sample rates of hundreds of samples per second
Synchronizing with Other Equipment
The ability to take samples for a very short time (as short as 250 µs) and the very flexible synchronization modes make it extremely convenient for applications such as measuring during a time domain EM system transmitter OFF time.
Precize PPS Synchronization
Uses fast (50MHz) dedicated hardware circuitry to capture the active PPS pulse edge and to provide the exact UTC Time of each sample if a GPS is connected to it. Thus its data can be synchronized with any other data having a time tag.
Flexible
- Provides ASCII data string output making it easy to embed in virtually any data acquisition system
- Can be easy configured to extract only the UTC time from the GGA string or to merge all the GPS data into its output string. Merging all the data into one string makes it possible to use only one RS232 port for both (Mag and GPS).
- Becomes a magnetic base station if combined with SDAS data logger.
- Becomes airborne data acquisition system if combined with SDAS1-PPC (the Pocket PC Data Logger) and one (for up to 8 differential analog channels) or two (for up to 16 differential analog channels) KANA8 (the Eight-Channel Analog Module).
- Provides easy settings change through the serial port.
Compact
The instrument is housed in an 6.8"W x 5.2" D x 2.2"H. aluminium box.
Front View
![[ KMAG4 Front View ]](images/kmag4-front_view.png)
ON
Power Supply LED
MAG1, MAG2, MAG3, MAG4
Two rows of BNC connectors. The bottom row is for the four sensors and the top one is for connecting an oscilloscope if necessary to observe the output signal of the associated sensor.
Rear View
![[ KMAG4 Rear View ]](images/kmag4-rear_view.png)
28VDC
A plastic circular four-pin power supply connector. The power supply should meet the requirements of the sensors used. 16AWG wires should be used for the power cable. Two wires (connected to pin1 and pin3 provide the positive power) and the other two (pin2 and pin4) provide the return. Below is the list of the other parts than are necessary to prepare the power cable:
| Item | Description | AMP Part # | Quantity |
|---|---|---|---|
| 1 | Plug Standard Sex | 206060-1 | 1 |
| 2 | Socket Contacts 18AWG-16AWG | 66181-1 | 4 |
| 3 | Cable Clamp | 206062-1 | 1 |
PORT1, PORT2, PORT3
Two different models are available for this instrument. Both models are the same from the hardware point of view. The difference is in the firmware and effects mainly the configuration of the DB9 connectors. The even firmware version numbers are reserved for the first model and the odd version numbers - for the second model.
EVEN VERSIONS
- PORT1 is used to connect the GPS. Its Baud rate could be 4800, 9600, 19200, 38400, 57600, 115200, 128000, 230400, 256000, 460800, 576000 or 768000 bits/sec and it is configured as follows:
No parity; 8 data bits; No flow control
- PORT3 provides the output data. Its Baud rate could be 9600, 19200, 38400, 57600, 115200, 128000, 230400, 256000, 460800, 576000 or 768000 bits/sec and it is configured as follows:
No parity; 8 data bits; No flow control
- The PPS signal from the GPS can be connected to pin 9 of any of the three DB9 connectors.
- The synchronization signal, used in External Trigger Mode, can be connected to pin 1 of any of the three DB9 connectors.
ODD VERSIONS
Provides selection of three options:
- PORT1 is for the output data and PORT2 - for the GPS data.
- PORT1 is for the output data and PORT3 - for the GPS data.
- PORT1 is for the output data, PORT2 - for the GPS data and PORT3 provides an additional RS232 receiver.
- The synchronization signal and the PPS are handled the same way as in the even versions.
Recommended Fuses
| Current Rating | Manufacturer | Part # |
|---|---|---|
| 2.5A | Littelfuse | 045202.5MR |