A method comprising: measuring a caliper of a sheet of material using a caliper sensor having first and second sensor modules; and adjusting the caliper measurement based on a transverse displacement between a first sensor component in the first sensor module and a second sensor component in the second sensor module, measured using at least one displacement sensor, to generate a corrected caliper measurement; wherein the first sensor module comprises: a first radiation source configured to direct first radiation towards a first side of the sheet; a cover having a first aperture configured to allow the first radiation to pass through the cover; and a Z-sensor configured to measure distance to the second sensor module; the second sensor module comprises: a second radiation source configured to direct second radiation towards a second side of the sheet; a dome having a second aperture configured to allow the second radiation to pass through the dome, the dome providing a target for the Z-sensor; and at least one holder configured to position at least one flag within the second aperture during standardization or calibration of the caliper sensor, the at least one flag having one or more known characteristics; the caliper of the sheet is measured using measurements of the first and second radiation that have interacted with the sheet and measurement of the Z-sensor, the first and second radiation is measured using a first and second distance measurement unit. measuring a caliper of a sheet of material using a caliper sensor having first and second sensor modules; and adjusting the caliper measurement based on a transverse displacement between a first sensor component in the first sensor module and a second sensor component in the second sensor module, measured using at least one displacement sensor, to generate a corrected caliper measurement; wherein the first sensor module comprises: a first radiation source configured to direct first radiation towards a first side of the sheet; a cover having a first aperture configured to allow the first radiation to pass through the cover; and a Z-sensor configured to measure distance to the second sensor module; a first radiation source configured to direct first radiation towards a first side of the sheet; a cover having a first aperture configured to allow the first radiation to pass through the cover; and a Z-sensor configured to measure distance to the second sensor module; the second sensor module comprises: a second radiation source configured to direct second radiation towards a second side of the sheet; a dome having a second aperture configured to allow the second radiation to pass through the dome, the dome providing a target for the Z-sensor; and at least one holder configured to position at least one flag within the second aperture during standardization or calibration of the caliper sensor, the at least one flag having one or more known characteristics; a second radiation source configured to direct second radiation towards a second side of the sheet; a dome having a second aperture configured to allow the second radiation to pass through the dome, the dome providing a target for the Z-sensor; and at least one holder configured to position at least one flag within the second aperture during standardization or calibration of the caliper sensor, the at least one flag having one or more known characteristics; the caliper of the sheet is measured using measurements of the first and second radiation that have interacted with the sheet and measurement of the Z-sensor, the first and second radiation is measured using a first and second distance measurement unit.