Constant speed device for tandem vibratory roller

The invention relates to a constant speed device for a tandem vibratory roller, comprising a shift control handle (3) and an A/D conversion circuit (5). In the device, a control panel of the tandem vibratory roller is provided with a constant speed mode switch (4), wherein the constant speed mode switch (4) is provided with two normally closed contacts and two normally open contacts; two input ends of the constant-speed mode switch (4) are connected with the OUT+ end and the OUT- end of the shift control handle (3); two normally closed ports (b, d) of the constant speed mode switch (4) are connected with two ends of the coil of the proportional electromagnetic valve on a running variable pump (6) respectively; two normally open ports (a, c) of the constant speed mode switch (4) are connected with 5VIN and AGND of the A/D conversion circuit (5) respectively; and two output ports of the A/D conversion circuit (5) are connected with two ends of the coil of the proportional electromagnetic valve on the running va