I need advice regarding the grounding of a 24V power supply!

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Hello, experts: I’m not very familiar with this issue related to the 24V grounding. I would like some advice: The main power supply provides 220V, which is used to power the switching power supply. After connecting L, N, and PE at the top of the switching power supply, the outputs on the bottom side are 24V+ and 24V-. It is connected below to a chromatograph with a voltage of 24V. The power terminals of the chromatograph have 3 connections: one for positive, one for negative, and one for grounding. I used a multimeter to check, and the ground on this chromatography power supply is connected to the chassis of the chromatograph. I used a 3-core power cable to connect the switching power supply to the chromatograph. As for the chromatograph side, it’s simple: + and -, plus ground, and that’s it. Well, here’s the question: Question 1: On the switch-mode power supply side, there are only 24V+ and 24V-. So where should the ground wire at this end be connected? Is it connected to the ground on the inner shell of the junction box? Won’t that be good for the earth then? Question 2: Why is the grounding at one end of the chromatograph connected to the chassis? In that case, doesn’t the 24V ground get connected to the earth? Can these 24V connections be connected to a 220V ground? I think there’s something wrong with this. Seeking advice, thank you!