TDS meter maintenance

I understand that for PH meters there are ph 4.0 and 7.0 to calibrate the solution. I am looking at a TDS meter and would like to know what I need to keep it calibrated. I saw a brand that had 1000ppm and 342 ppm solution. I then wanted to see the General Hydroponics version as they are usually more affordable and found only a 1500ppm solution. Can anyone help me with this? Thanks