DC Gaussmeter GM1-HS with Aluminium Carrying Case

The Alphalab GM1-HS DC Gaussmeter can be a very useful device for measuring residual magnetism in many types of materials including the strength of magnets that fall within its rated specification of .01 - 800 Gauss. The GM1-HS is one of two different models in this series of Gaussmeter that Alphalab sells. They have a GM1-ST which supports a high range of gaussian detection from .1G to 20KG. The difference between these two meters is the range. Although the GM1-ST has a higher gaussian range of detection the resolution to detect weaker fields is greatly reduced so this model might not be well suited for residual magnetic fields. Included in the shipment are the meter itself with a fixed 48" thin flat 3-conductor cable which has a hall-effect sensor fixed to the end. The hall-effect sensor is constructed in a manner which allows a small tab to be bent at a 90-degree angle if needed. As with most hall-effect sensors, you must orientate the sensor properly to get a correct reading. This is noted on the instruction sheet. Also including is a 2-sided instruction sheet and a 9V battery. The battery is not Alkaline but a standard Zinc-Carbon dry cell 9V which you may want to replace soon after with a better Alkaline for longer life.Construction of the housing is good but not great, this is about the only reason we gave this a 4 star. It is light and the plastics feel as if they could be damaged if dropped. The face of the unit is a press-on template with membrane buttons. This has the benefit of adding some protection against dirt and moisture getting into the controls. The display is LCD with no backlight, it is a 5 digit with decimal (xxx.xx), Low Battery indicator, and a DC indication in the upper left of the display. Since this only measures DC fields, this will obviously be a fixed indicator. The buttons are labeled as Power, Auto Zero, Offset Adjust -/+. Press and hold the Power button for a second or so to turn the unit on. Auto Zero will null the display to a neutral field and Offset Adjust will allow you to create an offset by .01G step resolution. It is recommended that before you take any measurements that you Auto Zero the unit in a Neutral or Zero Gauss environment. This will allow you to obtain the most accurate measurement possible. The Offset controls can be used for creating a zero point in a known magnetic field. For example, if you were measuring a fluctuation in a magnetic field which had a base gaussian value of 5G and you wanted to measure just the fluctuation of the field to 7G or 3G then by creating a zero offset in the 5G field you would only measure the field fluctuation as +2 or -2 gauss.In our tests here in the lab, we were quite surprised at the accuracy and performance of the unit itself. The ability to detect residual magnetic fields was quite impressive and the repeat tests were just about spot on. The performance from very strong magnetic fields such as neodymium to trace residual fields seemed to cause no offset or effect to the sensor or unit itself. However, it did need to be zeroed from time to time but this may have been due to magnetic fields here in the lab. A quick Auto Zero and we were back on track. The flat sensor cable is very flexible and easy to manipulate into small areas for field measurements. The hall-effect sensor is very small which makes it easy to get accurate measurements in tight areas.Internal construction is mostly SMT. There is a main board with a piggy-back LCD module attached to it. The revision of the PCB is A4. The description of the model has both HS and ST models silkscreened which is logical because the only difference I would assume would be calibration and hall-effect sensor. The case cover screens are self-tappers which are not our preferred method of anchor. We would much rather see threaded brass inserts, but we know it adds to the cost. We have attached pictures of both the exterior and interior of the unit.In conclusion, the GM1-HS and ST are very accurate gaussmeter's built by a reputable company. Alphalab has great technical support and their line of products are unique and useful at the same time. The build quality of many Alphalab products are very good, but we feel there is room for improvement. In a lab environment, these will no doubt give you years of solid performance but in the field I would not give it that same confidence mainly because of the enclosures. The unit is a solid performer giving us consistent results with little or no hassle. For it's intended purpose, we give this unit a thumbs up!