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Is your pressure transmitter one which outputs a current, such as 4-20 mA? If so, then the maximum distance is a function of conductor resistance and power supply compliance voltage. That is, if the conductor resistance is 100 ohms per 1000 feet, for example, and the power supply voltage is 12 volts, then the maximum resistance allowed is 600 ohms, limiting the distance to 3000 feet (300 ohms in each leg of a pair of conductors). Of course, most conductors are not that high in resistance, and some transmitters have a voltage drop across their terminals, so in the big scheme of things, neither is much of a problem.

In the case of a voltage output transmitter, there is very little current in the conductors, so the distance does have an effect, but not much. The greatest errors come from induced voltages, but properly grounded shielded conductors should eliminate most of that. For significant distances, it is much preferrable to use high output voltages rather than mV output (which is very subject to signal corruption).

As a rule of thumb, if you're using current as your signal (4-20mA), the maximum recommended cable length is 1000 meters. If you're using voltage, I think (never used voltage so I'm guessing) it's 50 meters.

This rule usually assumes a voltage supply of 24Vdc, no other load on the loop (transmitter is connected only to the controller/plc input and nothing else) and you're using a reasonable sized cable (18AWG or bigger).

If you increase the supply voltage, you can go farther. If math is not a problem for you, you can calculate the length of wire (using good ol' Ohm's Law). As another rule of thumb, any length that you obtain through calculation should be divided by at least two to give yourself a good margin.

thank you sir and if you dont mind please tell me the thumb rule

From Wikipedia:

Rule of Thumb - A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination.

Therefore, the rule that the maximum recommended distance of 1000 meters for 4-20mA signals is a rule-of-thumb because it is not strictly accurate or does not apply to every situation. It is a general rule. In short, you can deviate from it.

If you don't know how to calculate for the maximum distance then just take the 1000 meters as the rule and you should be fine.

I would agree with Vulcan "thumb rule" recommendations. Yes in cause your transmitter has current output you get less headache. For voltage output (its can be Volts and mV) try do not exceed distance over 50-100 metres. Though I had successful experience to connect 15 mV tranasmitters up to 200-300 metres. Of course your cable should be shielded and earthed properly. 6-wire circuit (in case you're using bridge) allows some increase distance.