{"id":3692,"date":"2023-03-13T08:09:41","date_gmt":"2023-03-13T15:09:41","guid":{"rendered":"https:\/\/www.rbdinstruments.com\/blog\/?p=3692"},"modified":"2023-03-13T08:30:29","modified_gmt":"2023-03-13T15:30:29","slug":"xps-analyzer-control-non-linearity-problem","status":"publish","type":"post","link":"https:\/\/www.rbdinstruments.com\/blog\/xps-analyzer-control-non-linearity-problem\/","title":{"rendered":"XPS analyzer control non-linearity problem"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">The 80-360 and 80-365\/366 analyzer controls provide all the voltages to the 10-360 spherical capacitor analyzer that is used on many PHI (Physical Electronics) XPS systems.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><a href=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?ssl=1\"><img data-recalc-dims=\"1\" decoding=\"async\" data-attachment-id=\"3697\" data-permalink=\"https:\/\/www.rbdinstruments.com\/blog\/xps-analyzer-control-non-linearity-problem\/80-365-boards\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?fit=2000%2C1500&amp;ssl=1\" data-orig-size=\"2000,1500\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;1&quot;}\" data-image-title=\"80-365-boards\" data-image-description=\"\" data-image-caption=\"\" data-large-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?fit=584%2C438&amp;ssl=1\" src=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/plugins\/jquery-image-lazy-loading\/images\/grey.gif?w=584&#038;ssl=1\" data-original=\"https:\/\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards-1024x768.jpg\" alt=\"\" class=\"lazy wp-image-3697\"\/><noscript><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" width=\"584\" height=\"438\" data-attachment-id=\"3697\" data-permalink=\"https:\/\/www.rbdinstruments.com\/blog\/xps-analyzer-control-non-linearity-problem\/80-365-boards\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?fit=2000%2C1500&amp;ssl=1\" data-orig-size=\"2000,1500\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;1&quot;}\" data-image-title=\"80-365-boards\" data-image-description=\"\" data-image-caption=\"\" data-large-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?fit=584%2C438&amp;ssl=1\" src=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?resize=584%2C438&#038;ssl=1\" alt=\"\" class=\"wp-image-3697\" srcset=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?resize=1024%2C768&amp;ssl=1 1024w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?resize=300%2C225&amp;ssl=1 300w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?resize=768%2C576&amp;ssl=1 768w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?resize=1536%2C1152&amp;ssl=1 1536w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?resize=400%2C300&amp;ssl=1 400w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?w=2000&amp;ssl=1 2000w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?w=1168&amp;ssl=1 1168w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/80-365-boards.jpg?w=1752&amp;ssl=1 1752w\" sizes=\"auto, (max-width: 584px) 100vw, 584px\" \/><\/noscript><\/a><figcaption>80-365 boards  Retard board is third from left<\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">The retard voltage is used to slow down electrons and is essentially the sweep voltage.&nbsp; In conjunction with the pass energy supply, the retard voltage controls the energy of the electrons that are being passed through the analyzer and into the electron multiplier and counting circuitry.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">I recently had an interesting problem with a retard board on an 80-360 analyzer controller.&nbsp; The issue was that the retard board output voltage was not linear.&nbsp;&nbsp; Part of the calibration procedure for the retard board is to test the voltage at 11 specific voltages ranging from 253.6 volts to 1253.6 volts in increments of 100 volts.&nbsp; This is a convenient way to confirm that the retard supply is linear.&nbsp; The table below shows the hex commands that are used to set the voltages and the expected results.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><a href=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Expected-Retard-Votlage-Measurements.jpg?ssl=1\"><img data-recalc-dims=\"1\" decoding=\"async\" data-attachment-id=\"3694\" data-permalink=\"https:\/\/www.rbdinstruments.com\/blog\/xps-analyzer-control-non-linearity-problem\/expected-retard-votlage-measurements\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Expected-Retard-Votlage-Measurements.jpg?fit=846%2C847&amp;ssl=1\" data-orig-size=\"846,847\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}\" data-image-title=\"Expected-Retard-Votlage-Measurements\" data-image-description=\"\" data-image-caption=\"\" data-large-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Expected-Retard-Votlage-Measurements.jpg?fit=584%2C585&amp;ssl=1\" src=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/plugins\/jquery-image-lazy-loading\/images\/grey.gif?w=584&#038;ssl=1\" data-original=\"https:\/\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Expected-Retard-Votlage-Measurements.jpg\" alt=\"\" class=\"lazy wp-image-3694\"\/><noscript><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" width=\"584\" height=\"585\" data-attachment-id=\"3694\" data-permalink=\"https:\/\/www.rbdinstruments.com\/blog\/xps-analyzer-control-non-linearity-problem\/expected-retard-votlage-measurements\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Expected-Retard-Votlage-Measurements.jpg?fit=846%2C847&amp;ssl=1\" data-orig-size=\"846,847\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}\" data-image-title=\"Expected-Retard-Votlage-Measurements\" data-image-description=\"\" data-image-caption=\"\" data-large-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Expected-Retard-Votlage-Measurements.jpg?fit=584%2C585&amp;ssl=1\" src=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Expected-Retard-Votlage-Measurements.jpg?resize=584%2C585&#038;ssl=1\" alt=\"\" class=\"wp-image-3694\" srcset=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Expected-Retard-Votlage-Measurements.jpg?w=846&amp;ssl=1 846w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Expected-Retard-Votlage-Measurements.jpg?resize=300%2C300&amp;ssl=1 300w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Expected-Retard-Votlage-Measurements.jpg?resize=150%2C150&amp;ssl=1 150w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Expected-Retard-Votlage-Measurements.jpg?resize=768%2C769&amp;ssl=1 768w\" sizes=\"auto, (max-width: 584px) 100vw, 584px\" \/><\/noscript><\/a><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">In this particular case, the output voltages were close to correct at some points, but way off at other points as shown below. This non-linearity would present itself as inconsistent peak widths in the data as a function of kinetic energy.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><a href=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Actual-Retard-Votlage-Measurements.jpg?ssl=1\"><img data-recalc-dims=\"1\" decoding=\"async\" data-attachment-id=\"3695\" data-permalink=\"https:\/\/www.rbdinstruments.com\/blog\/xps-analyzer-control-non-linearity-problem\/actual-retard-votlage-measurements\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Actual-Retard-Votlage-Measurements.jpg?fit=846%2C847&amp;ssl=1\" data-orig-size=\"846,847\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;1&quot;}\" data-image-title=\"Actual-Retard-Votlage-Measurements\" data-image-description=\"\" data-image-caption=\"\" data-large-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Actual-Retard-Votlage-Measurements.jpg?fit=584%2C585&amp;ssl=1\" src=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/plugins\/jquery-image-lazy-loading\/images\/grey.gif?w=584&#038;ssl=1\" data-original=\"https:\/\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Actual-Retard-Votlage-Measurements.jpg\" alt=\"\" class=\"lazy wp-image-3695\"\/><noscript><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" width=\"584\" height=\"585\" data-attachment-id=\"3695\" data-permalink=\"https:\/\/www.rbdinstruments.com\/blog\/xps-analyzer-control-non-linearity-problem\/actual-retard-votlage-measurements\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Actual-Retard-Votlage-Measurements.jpg?fit=846%2C847&amp;ssl=1\" data-orig-size=\"846,847\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;1&quot;}\" data-image-title=\"Actual-Retard-Votlage-Measurements\" data-image-description=\"\" data-image-caption=\"\" data-large-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Actual-Retard-Votlage-Measurements.jpg?fit=584%2C585&amp;ssl=1\" src=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Actual-Retard-Votlage-Measurements.jpg?resize=584%2C585&#038;ssl=1\" alt=\"\" class=\"wp-image-3695\" srcset=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Actual-Retard-Votlage-Measurements.jpg?w=846&amp;ssl=1 846w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Actual-Retard-Votlage-Measurements.jpg?resize=300%2C300&amp;ssl=1 300w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Actual-Retard-Votlage-Measurements.jpg?resize=150%2C150&amp;ssl=1 150w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/Actual-Retard-Votlage-Measurements.jpg?resize=768%2C769&amp;ssl=1 768w\" sizes=\"auto, (max-width: 584px) 100vw, 584px\" \/><\/noscript><\/a><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">These results at first glance look like a bit problem.&nbsp; That is, the digital to analog convertor (DAC) voltages are likely off.&nbsp; The DAC used in the retard board circuit is a 16 bit DAC and the output voltages should follow the voltages listed&nbsp; below.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><a href=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/DAC-voltages.jpg?ssl=1\"><img data-recalc-dims=\"1\" decoding=\"async\" data-attachment-id=\"3696\" data-permalink=\"https:\/\/www.rbdinstruments.com\/blog\/xps-analyzer-control-non-linearity-problem\/dac-voltages\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/DAC-voltages.jpg?fit=501%2C487&amp;ssl=1\" data-orig-size=\"501,487\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}\" data-image-title=\"DAC-voltages\" data-image-description=\"\" data-image-caption=\"\" data-large-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/DAC-voltages.jpg?fit=501%2C487&amp;ssl=1\" src=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/plugins\/jquery-image-lazy-loading\/images\/grey.gif?w=584&#038;ssl=1\" data-original=\"https:\/\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/DAC-voltages.jpg\" alt=\"\" class=\"lazy wp-image-3696\"\/><noscript><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" width=\"501\" height=\"487\" data-attachment-id=\"3696\" data-permalink=\"https:\/\/www.rbdinstruments.com\/blog\/xps-analyzer-control-non-linearity-problem\/dac-voltages\/\" data-orig-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/DAC-voltages.jpg?fit=501%2C487&amp;ssl=1\" data-orig-size=\"501,487\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}\" data-image-title=\"DAC-voltages\" data-image-description=\"\" data-image-caption=\"\" data-large-file=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/DAC-voltages.jpg?fit=501%2C487&amp;ssl=1\" src=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/DAC-voltages.jpg?resize=501%2C487&#038;ssl=1\" alt=\"\" class=\"wp-image-3696\" srcset=\"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/DAC-voltages.jpg?w=501&amp;ssl=1 501w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/DAC-voltages.jpg?resize=300%2C292&amp;ssl=1 300w, https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/DAC-voltages.jpg?resize=309%2C300&amp;ssl=1 309w\" sizes=\"auto, (max-width: 501px) 100vw, 501px\" \/><\/noscript><\/a><figcaption>DAC Voltages<\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">However, the DAC voltages were fine.&nbsp; The retard voltage circuit comprises the DAC which drives a precision operational amplifier that in turn drives a high voltage switching supply.&nbsp; Some precision high voltage resistors are&nbsp; used to provide feedback.&nbsp; The next most likely component that might be non-linear was the <a href=\"https:\/\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/OP07.pdf\" data-type=\"attachment\" data-id=\"3700\">OP07<\/a> ultra-low offset operational amplifier (op amp).&nbsp; The OP07 was replaced but did not solve the problem.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The next most likely cause of the non-linearity problem was the feedback resistors. &nbsp;There is a total of 5 of these <a href=\"https:\/\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/SX3730-5W-resistor.pdf\" data-type=\"attachment\" data-id=\"3699\">SX3730 5 watt wire wound high precision axial resistors<\/a> in series.&nbsp; To accurately measure those resistors, you need to lift one end off the circuit board.&nbsp; Using my Fluke multimeter, I tested the resistance of each resistor and they all checked out as OK.&nbsp; Ideally you will see very close to 1.0 megohms, but it might be off by .05 megohms.&nbsp;When a resistor is bad it will be open or be off by as much as .5 megohms. So, it seemed that the feedback resistors were OK as well.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">That left not much in the circuit other than a few potentiometers.&nbsp;After spending some more time retesting all the components, I came to the conclusion that it had to be one of those feedback resistors.&nbsp;<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">To test that theory I removed all 5 of the <a href=\"https:\/\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/SX3730.jpg\" data-type=\"attachment\" data-id=\"3703\">SX3730<\/a> 1 megohm feedback resistors and replaced them with a single 5 meg ohm resistor.&nbsp; And that worked!&nbsp;&nbsp; So now I knew for sure that one of those 5 feedback resistors was the problem.&nbsp; I measured the resistance of each resistor, and they looked OK.&nbsp; But then I realized that the non-linearity is a function of the voltage applied to the resistor. At some voltages the resistance was OK, but at other voltages the resistance was off.&nbsp;<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">I then decided to measure the resistance value again using a megohmmeter.&nbsp; The model that I used was a Protek DI-2000M.&nbsp; This megohmmeter (also called an insulation tester) puts 500 V across the resistor when measuring the resistance. I hoped that by putting 500V across the resistor that I would be able to see a greater difference in the resistance values. And that worked out as expected.&nbsp; One of the resistors showed only 965 Kohms with the megohmmeter and 995 Kohms with the Fluke.&nbsp;I replaced that resistor and the calibration was perfect.&nbsp; \ud83d\ude0a<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In hindsight, duh. Since the gain of the circuit was changing as a function of the non-linearity of one resistor, the lesson is that when checking the resistance of suspected non-linear resistors, always use a megohmmeter since that will put much more voltage across the resistor than what a normal DVM will put out. Better yet, if possible, use the highest voltage that the resistor is rated for.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If your 80-360 or 80-365\/366 analyzer control is not functioning properly and you need some help, please contact RBD Instruments for assistance as needed.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>80-360 analyzer control retard voltage non-linearity issue and solution <a href=\"https:\/\/www.rbdinstruments.com\/blog\/xps-analyzer-control-non-linearity-problem\/\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":3703,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[162],"tags":[408,376,410,409],"class_list":["post-3692","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-operation-and-calibration-procedures","tag-80-360","tag-80-365","tag-resistor-non-linearity","tag-retard-voltage"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/www.rbdinstruments.com\/blog\/wp-content\/uploads\/2023\/03\/SX3730.jpg?fit=756%2C756&ssl=1","jetpack_shortlink":"https:\/\/wp.me\/p2DEXo-Xy","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.rbdinstruments.com\/blog\/wp-json\/wp\/v2\/posts\/3692","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.rbdinstruments.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.rbdinstruments.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.rbdinstruments.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.rbdinstruments.com\/blog\/wp-json\/wp\/v2\/comments?post=3692"}],"version-history":[{"count":2,"href":"https:\/\/www.rbdinstruments.com\/blog\/wp-json\/wp\/v2\/posts\/3692\/revisions"}],"predecessor-version":[{"id":3710,"href":"https:\/\/www.rbdinstruments.com\/blog\/wp-json\/wp\/v2\/posts\/3692\/revisions\/3710"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.rbdinstruments.com\/blog\/wp-json\/wp\/v2\/media\/3703"}],"wp:attachment":[{"href":"https:\/\/www.rbdinstruments.com\/blog\/wp-json\/wp\/v2\/media?parent=3692"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rbdinstruments.com\/blog\/wp-json\/wp\/v2\/categories?post=3692"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rbdinstruments.com\/blog\/wp-json\/wp\/v2\/tags?post=3692"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}