KMAG4 - 260MHz Four-Sensor Magnetometer Counter

Features
Front View
Rear View

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

Compact

The instrument is housed in an 6.8"W x 5.2" D x 2.2"H. aluminium box.

Front View

Sensor Power Indicator Oscilloscope Connector Oscilloscope Connector Oscilloscope Connector Oscilloscope Connector Sensor Connector Sensor Connector Sensor Connector Sensor Connector [ KMAG4 Front View ]

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

Power Supply Connector Main RS-232 Port GPS RS-232 Port PPS signal from the GPS [ KMAG4 Rear View ]

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

No parity; 8 data bits; No flow control

No parity; 8 data bits; No flow control

ODD VERSIONS

Provides selection of three options:

Recommended Fuses

Current Rating Manufacturer Part #
2.5A Littelfuse 045202.5MR