WEBVTT 00:00:06.704 --> 00:00:13.204 We’re demonstrating ultra-high magnetic field reliability testing for NVE’s medical-grade switch sensors. 00:00:13.465 --> 00:00:19.941 The parts being tested are NVE's 1.5 volt and 3 volt medical-grade magnetic switch sensors. 00:00:20.123 --> 00:00:33.228 The PCB on the right holds the five pairs of sensors being tested: the BHL925SP, the BD027, the BD032, BD121, and the BD129. 00:00:34.198 --> 00:00:41.590 All NVE medical-grade sensors are MRI safe, meaning they cannot be damaged by magnetic fields up to 9 tesla. 00:00:41.833 --> 00:00:50.127 However, some sensors cannot maintain the correct output state at high field strengths, beginning usually at 40 millitesla, or 400 gauss. 00:00:50.317 --> 00:00:57.401 Sensors that are designed to maintain the correct output at large fields are MRI correct, in addition to being MRI safe. 00:00:57.401 --> 00:00:59.103 This is what we are testing for. 00:01:00.000 --> 00:01:08.108 The device used to produce the large magnetic field is a liquid helium-cooled superconducting magnet made by the Janis Research Company. 00:01:08.591 --> 00:01:16.599 The particular system you see here is owned by the Department of Chemical Engineering and Materials Science at the University of Minnesota, Twin Cities. 00:01:17.424 --> 00:01:22.544 The Janis magnet produces magnetic fields as strong as those produced in an MRI machine. 00:01:22.945 --> 00:01:27.874 This is a clip demonstrating the strength of an MRI’s magnetic field with a steel chair. 00:01:34.694 --> 00:01:41.194 The part of the Janis system above the floor is only cryogenics equipment; the actual magnet is slightly below the floor. 00:01:41.540 --> 00:01:47.307 Because the magnet is under the floor, this long rod must be used to place our parts close to the magnet. 00:01:47.564 --> 00:01:53.461 The PCB holding the parts is placed into this DIP socket at the end of the rod, which you can see happening here. 00:01:59.233 --> 00:02:02.007 The rod is then inserted into the Janis system. 00:02:12.266 --> 00:02:17.766 The voltage pins of the magnetic switch sensors are broken out to this box through the wiring of the rod, 00:02:17.766 --> 00:02:21.690 and BNC cables are connected for individual part voltage measurements. 00:02:23.937 --> 00:02:28.321 The other ends of the cables are connected to power and a data acquisition card. 00:02:30.228 --> 00:02:34.368 Here, we have the wiring set up, and we are ready to begin taking data. 00:02:34.661 --> 00:02:38.015 The Janis system is here, behind the BNC cables. 00:02:38.348 --> 00:02:43.108 The magnetic field magnitude that the parts are subjected to is displayed here. 00:02:43.324 --> 00:02:47.374 And the LabView front panel with the output voltage of all the parts is here. 00:02:47.588 --> 00:02:52.295 The top left and top right LabView charts can be ignored; they are for calibration. 00:02:52.614 --> 00:02:55.451 The other ten charts show the sensors of interest. 00:02:57.609 --> 00:03:01.238 The BD027 parts are our control sample. 00:03:02.076 --> 00:03:05.388 Here, we begin increasing the magnetic field. 00:03:11.084 --> 00:03:15.000 All the parts switch to their ON state, which results in a LOW voltage output. 00:03:15.199 --> 00:03:21.322 You may have noticed that the BD027s started in the ON state, then went OFF, and then ON again, 00:03:21.322 --> 00:03:25.079 while the other 8 parts simply started in the OFF state and then switched ON. 00:03:25.205 --> 00:03:33.070 This is because these particular BD027s have a slightly lower operate point than the other parts, and, being omnipolar, were 00:03:33.070 --> 00:03:39.126 switched ON by a magnetic field offset of a couple gauss in the direction opposite to the intended field direction. 00:03:39.226 --> 00:03:43.944 This field offset quickly becomes negligible as we approach large field values. 00:03:44.033 --> 00:03:47.402 At 500 gauss, all 10 parts are in the ON state. 00:03:52.717 --> 00:04:02.583 At 1 kilogauss, or 0.1 tesla, the 8 MRI-correct parts remain ON, but the BD027 control samples switch back to the OFF state. 00:04:11.172 --> 00:04:14.910 This continues all the way up to 90 kilogauss, or 9 tesla. 00:04:15.000 --> 00:04:19.740 An impressive feat, demonstrating their suitability for withstanding MRI fields. 00:04:27.958 --> 00:04:34.133 Here is a close up of the charts. The MRI-correct parts are the ones highlighted in blue. We can see they are 00:04:34.133 --> 00:04:39.224 in the ON state because the open-drain outputs are sinking current, resulting in a LOW output. 00:04:39.660 --> 00:04:48.061 The bottom left and bottom right charts are the BD027s. They have a 2 volt, HIGH, output, meaning they are in the OFF state, despite the large field. 00:04:49.267 --> 00:04:51.787 We now decrease the field back towards 0. 00:04:57.220 --> 00:05:03.539 Around 800 gauss, the BD027s switch back to the correct state of 0 volts output. 00:05:08.285 --> 00:05:15.774 At around 30 gauss, all parts switch back to the OFF state, resulting in a HIGH output of 2 volts, which is correct behavior. 00:05:18.690 --> 00:05:24.188 Here is a close up of the charts at 0 field, with the 8 MRI-correct parts highlighted again. 00:05:36.511 --> 00:05:42.389 NVE's medical-grade magnetic switch sensors have operate points as low as 1.3 millitesla. 00:05:42.636 --> 00:05:45.399 Have low hysteresis to prevent magnetic latching. 00:05:45.614 --> 00:05:48.757 Are very low power; as low as 30 nanowatts. 00:05:48.912 --> 00:05:53.681 Operate in a temperature range from -40 to 125 degrees Celsius. 00:05:53.839 --> 00:05:59.626 And come in a miniature 1.1 mm × 1.1 mm DFN4 package. 00:06:00.368 --> 00:06:05.005 Call, click, or email for more information about NVE's remarkable sensors. 00:06:05.788 --> 00:06:11.088 Lastly, I would like to thank the University of Minnesota, Twin Cities Department of Chemical Engineering and 00:06:11.088 --> 00:06:16.591 Materials Science for allowing and aiding our use of their cryogenic superconducting magnet.