A pressure transmitter for measuring a pressure of a process fluid, the pressure transmitter comprising: a pressure sensor for sensing the pressure of the process fluid; a hydraulic relay system for providing a communication channel between the process fluid and the pressure sensor; a pressure sensor fill fluid in the hydraulic relay system, the pressure sensor fill fluid comprising: a first hydraulic fluid for transmitting a change in the pressure of the process fluid to the sensor; and a first volume of nano-particles suspended within the first hydraulic fluid for altering properties of the pressure sensor fill fluid; and the pressure transmitter characterised by further comprising: a remote seal system comprising: a capillary tube (34A, 34B) fluidically connected to the hydraulic relay system for extending reach of the hydraulic relay system; a remote seal fill fluid within the capillary tube (34A, 34B), the remote seal fill fluid comprising: a second hydraulic fluid for communicating the pressure of the process fluid through the capillary tube (34A, 34B) to the first hydraulic fluid for transmitting a change in the pressure of the process fluid to the sensor; and a second volume of nano-particles suspended within the second hydraulic fluid for altering properties of the remote seal fill fluid. a pressure sensor for sensing the pressure of the process fluid; a hydraulic relay system for providing a communication channel between the process fluid and the pressure sensor; a pressure sensor fill fluid in the hydraulic relay system, the pressure sensor fill fluid comprising: a first hydraulic fluid for transmitting a change in the pressure of the process fluid to the sensor; and a first volume of nano-particles suspended within the first hydraulic fluid for altering properties of the pressure sensor fill fluid; and the pressure transmitter characterised by further comprising: a remote seal system comprising: a capillary tube (34A, 34B) fluidically connected to the hydraulic relay system for extending reach of the hydraulic relay system; a remote seal fill fluid within the capillary tube (34A, 34B), the remote seal fill fluid comprising: a second hydraulic fluid for communicating the pressure of the process fluid through the capillary tube (34A, 34B) to the first hydraulic fluid for transmitting a change in the pressure of the process fluid to the sensor; and a second volume of nano-particles suspended within the second hydraulic fluid for altering properties of the remote seal fill fluid. a first hydraulic fluid for transmitting a change in the pressure of the process fluid to the sensor; and a first volume of nano-particles suspended within the first hydraulic fluid for altering properties of the pressure sensor fill fluid; and the pressure transmitter characterised by further comprising: a remote seal system comprising: a capillary tube (34A, 34B) fluidically connected to the hydraulic relay system for extending reach of the hydraulic relay system; a remote seal fill fluid within the capillary tube (34A, 34B), the remote seal fill fluid comprising: a second hydraulic fluid for communicating the pressure of the process fluid through the capillary tube (34A, 34B) to the first hydraulic fluid for transmitting a change in the pressure of the process fluid to the sensor; and a second volume of nano-particles suspended within the second hydraulic fluid for altering properties of the remote seal fill fluid. a capillary tube (34A, 34B) fluidically connected to the hydraulic relay system for extending reach of the hydraulic relay system; a remote seal fill fluid within the capillary tube (34A, 34B), the remote seal fill fluid comprising: a second hydraulic fluid for communicating the pressure of the process fluid through the capillary tube (34A, 34B) to the first hydraulic fluid for transmitting a change in the pressure of the process fluid to the sensor; and a second volume of nano-particles suspended within the second hydraulic fluid for altering properties of the remote seal fill fluid. a second hydraulic fluid for communicating the pressure of the process fluid through the capillary tube (34A, 34B) to the first hydraulic fluid for transmitting a change in the pressure of the process fluid to the sensor; and a second volume of nano-particles suspended within the second hydraulic fluid for altering properties of the remote seal fill fluid.