Sat, Chit and Ananda are one. Atman is partless and homogeneous. The three characteristics Sat, Chit and Ananda are not distinct from one another. They are coeval and coexistent with Atman. Sat-Chit-Ananda signify the one Atman. Sat is Chit. Sat is Ananda. Chit is Sat. Chit is Ananda. Ananda is Sat. Ananda is Chit. You cannot split up Sat-Chit-Ananda into three separate entities, just as you cannot separate light, heat and luminosity from fire.
Atman is Sat
Atman is Sat. That which exists in the past, present and future, which has no beginning, middle and end, which is unchanging, which is not conditioned in time, space and causation, which exists during Jagrat, Svapna and Sushupti, which is of the nature of one homogeneous essence (Sada Ekarasa, Sada Ekarupa) is Sat. This is found in Atman. Srutis emphatically declare: Sat only was prior to the evolution of this universe.
Atman is Chit
Atman is Chit because he shines by himself without the help of any other light and illuminates the entire universe by his own light.
The mind is finite and inert. He has no independent intelligence. He is not self-luminous. The brilliance of him is borrowed from the Light of the fountain. He is subject to various limitations and changes. He is only an inert product of subtle matter. Only the Atman is the source of Chit. The mind is also perceived by Chit. The mind has a beginning and an end.
The external universe, however varied and large it may be, is after all only inert matter. It cannot be the object of our perception unless we cast upon it the flow of light from our consciousness; he can never know us. It is enlightened only by us. It can never enlighten us.
Atman is Ananda
Ananda is that bliss that is eternal, uncaused and incomparable. It is the true nature of Atman.
But the supreme bliss of Brahman has no degrees. It is infinite or unlimited because there is nothing superior to it. The bliss of deep sleep has no degrees.
Brahman bliss cannot be adequately expressed in words. It has to be felt and realized through the direct realization of the Self. Although we experience it, it is not an experience like the enjoyment of an object, because you are then an incarnation of bliss itself.
All miseries come to an end when one realizes (realizes) the Atman. Therefore the Atman must be an embodiment of bliss. Sat is Chit. Sat is Ananda too.
He who has realized this Sat-Chit-Ananda Atman is a liberated sage. He has nothing else to learn, he has nothing else to do, he has nothing else to gain. All his wishes are satisfied. He has obtained all the worlds. He is freed from the clutches of death. He achieves immortality.